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Document:	VAX Volume Shadowing Manual
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VAX Volume Shadowing
Manual
Order Number: AA-LB 18A-TE

April 1988
This manual describes VAX Volume Shadowing.

Revision/Update Information:

This manual supersedes the VAX/VMS
Volume Shadowing Manual,
Version 1.0.

Operating System and Version: VMS Version 5.0
Software Version:

digital equipment corporation
maynard, massachusetts

VAX Volume Shadowing Version 5.0

April 1988
The information in this document is subject to change without notice and should
not be construed as a commitment by Digital Equipment Corporation. Digital
Equipment Corporation assumes no responsibility for any errors that may appear
in this document.
The software described in this document is furnished under a license and may be
used or copied only in accordance with the terms of such license.
No responsibility is assumed for the use or reliability of software on equipment
that is not supplied by Digital Equipment Corporation or its affiliated companies.
Copyright © 1988 by Digital Equipment Corporation
All Rights Reserved.
Printed in U.S.A.
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requests the user's critical evaluation to assist in preparing future documentation.
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Contents
PREFACE

CHAPTER 1 INTRODUCTION TO VAX VOLUME SHADOWING

1-1

1.1

OVERVIEW

1-1

1.2

VOLUME SHADOWING TERMS

1-2

1.3

HARDWARE REQUIREMENTS

1-3

1.4

MOUNTING A SHADOW SET

1-6

1.5

SHADOW SET CHANGES

1-7

1.6

EXAMINING A SHADOW SET

1-8

1.7

ADDING AND REMOVING SHADOW SET MEMBERS

1-9

1.8

DISSOLVING A SHADOW SET

1-9

1.9

SHADOW SETS AS SYSTEM DISKS AND IN VAXCLUSTERS

1-10

CHAPTER 2 THE COMMAND-LEVEL INTERFACE
2.1
2.1.1
2.1.2
2.1.3
2.1.4
2.1.4.1
2.1.4.2
2.1.4.3

2.1.5
2.1.5.1

CREATING A SHADOW SET WITH THE MOUNT UTILITY
Mounting a Files-11 Shadow Set
MOUNT Examples
Mounting a Foreign Shadow Set
Files-11 Copy Operations
Full Copy • 2-6
Merge Copy • 2-6
Determining the Correct Copy Operation • 2-6
Qualifiers
The /CONFIRM Qualifier (Files-11 Shadow Sets) • 2-8

2-1
2-1
2-2
2-4
2-4
2-6

2-7

Contents

2.1.5.2
2.1.5.3
2. 1.5.4
2.1.5.5

The /COPY Qualifier (Files-11 Shadow Sets) • 2-9
The /OVERRIDE=SHADOW_MEMBERSHIP Qualifier • 2-10
Using MOUNT /OVERRIDE=IDENTIFICA TION • 2-11
Using MOUNT/NOMOUNT_VERIFICATION • 2-11

2.2

ADDING MEMBERS TO A SHADOW SET

2-11

2.3

REMOVING MEMBERS FROM A SHADOW SET

2-12

2.4

DISMOUNTING AND DISSOLVING A SHADOW SET

2-13

2.5
2.5.1
2.5.2
2.5.3

EXAMINING A SHADOW SET WITH THE DCL COMMAND
SHOW DEVICES
Listing Shadow Set Virtual Units
Listing Shadow Set Members
SHOW DEVICES Examples

2-14
2-14
2-14
2-15

2.6

USING THE F$GETDVI LEXICAL FUNCTION

2-17

2.7
2.7.1
2.7.2
2.7.3

PERFORMING BACKUP OPERATIONS ON A SHADOW SET
Using a Shadow Set Copy as a Backup
Using the VMS Backup Utility
Using BACKUP/IMAGE on a Shadow Set

2-18
2-18
2-19
2-20

2.8

MAINTAINING A SHADOW SET

2-22

CHAPTER 3 PERFORMING SHADOW SET OPERATIONS WITH
SYSTEM SERVICES
3.1
3.1.1
3.1.2
3.1.3
3.1.4

3.2
3.2.1
3.2.2
3.2.3
vi

3-1

USING $MOUNT TO CREATE AND MOUNT SHADOW SETS
$MOUNT Shadow Set Item Codes
Constructing the $MOUNT Item List
Examples of $MOUNT Item Lists
Evaluating Condition Values Returned by $DISMOU,
$MOUNT, and $QIO

3-1
3-2
3-4
3-5

USING $DISMOU TO DISMOUNT SHADOW SETS
Removing Member Units from Shadow Sets
Dismounting and Dissolving Shadow Sets
Setting $DISMOU Flags in Shadow Set Operations

3-8
3-9
3-9
3-11

3-8

3.3

USING $GETDVI TO OBTAIN INFORMATION ABOUT
SHADOW SETS
$G ETDVI Shadow Set Item Codes
Obtaining the Names of All Members of a Shadow Set

3-11
3-11
3-13

CHAPTER4 LICENSING, ENABLING, AND MANAGING VAX
VOLUME SHADOWING

4-1

3.3.1
3.3.2

4.1

REGISTERING THE VOLUME SHADOWING PRODUCT
AUTHORIZATION KEY (PAK)

4-1

SETTING THE SYSGEN PARAMETER FOR VOLUME
SHADOWING

4-2

4.3

USING VOLUME SHADOWING ON THE SYSTEM DISK

4-2

4.4

BOOTING FROM A SYSTEM DISK SHADOW SET

4-3

4.5

UPGRADING A SYSTEM THAT USES A SYSTEM DISK
SHADOW SET

4-5

PERFORMANCE INFORMATION FOR VOLUME
SHADOWING

4-8

4.2

4.6

4.7
4.7.1
4.7.2

4.8
4.8.1
4.8.2
4.8.3

STANDALONE BACKUP AND VOLUME SHADOWING
lncompatiblities Between Shadow Sets and Standalone
BACKUP
Using Standalone BACKUP on Disks That Are Former
Shadow Set Members
VOLUME SHADOWING IN MIXED-INTERCONNECT
CLUSTERS
Mounting Shadow Sets in a Mixed-Interconnect VAXcluster
Configuration
Dismounting Shadow Sets in a Mixed-Interconnect
VAXcluster Configuration
Using Shadow Sets as Satellite System Disks

4-8
4-8
4-9

4-9
4-10
4-10
4-11

vii

Contents

APPENDIX A MESSAGES

A-1

A.1

MOUNT VERIFICATION STATUS MESSAGES

A-1

A.2

MOUNT VERIFICATION MESSAGES THAT APPLY TO
SHADOW SETS

A-2

MOUNT MESSAGES THAT APPLY TO SHADOW SETS

A-2

A.3

APPENDIX B MOUNT QUALIFIERS FOR VOLUME SHADOWING
/CONFIRM
/COPY
/OVERRIDE
/SHADOW

B-1

B-2
B-4
B-6
B-7

APPENDIX C SYSTEM SERVICES ITEM CODES FOR VOLUME
SHADOWING

C-1

INDEX

EXAMPLES
4-1

Example of a Product Authorization Key (PAK)

4-1

4-2

Shadow Set as Seen from Boot Server

4-9

4-3

Shadow Set as Seen from Satellite

4-10

FIGURES

viii

1-1

Elements of a Shadow Set (One VAX -

One HSC)

1-2

Elements of a Shadow Set (One VAX -Two HSCs)

1-3
4-1

Elements of a Shadow Set (A VAXcluster Booting from a System Disk Shadow Set

Two HSCs)

1-4
1-5
1-6

4-4

Contents

TABLES
2-1
4-1

F$GETDVI Items for Volume Shadowing

2-17

Names of Default Boot Command Procedures

4-5

Preface
The VAX Volume Shadowing Manual describes how to use the volume
shadowing option.

Intended Audience
This manual is intended for VMS programmers, system managers, and
general users.

Document Structure
The VAX Volume Shadowing Manual consists of four chapters and three
appendixes.
Chapter 1 gives an introduction to volume shadowing.
Chapter 2 describes the VMS utilities and DCL commands used to mount,
maintain, and dismount volume shadowing sets.
Chapter 3 describes the programming interface to VAX Volume Shadowing,
which consists of modifications to three system service routines.
Chapter 4 briefly explains license registration and describes how to manage
VAX Volume Shadowing.
Appendix A lists the mount verification messages and the Mount Utility
messages related to volume shadowing.
Appendix B is a summary of the Mount Utility qualifiers for volume
shadowing, designed to be inserted into the VMS Mount Utility Manual.
Appendix C is a summary of the system services item codes for volume
shadowing, designed to be inserted into the VMS System Services Reference

Manual.

Associated Documents
The following documents contain information related to this manual:

•
•
•
•

Introduction to VMS System Management

•

Guide to Setting Up a VMS System

•
•
•
•

Guide to Maintaining a VMS System

VMS License Management Utility Manual
VMS VAXcluster Manual
Guide to VMS Files and Devices

VMS DCL Dictionary
VMS Mount Utility Manual
VMS Backup Utility Manual
xi

Preface

•

VMS System Services Reference Manual

•

VMS System Messages and Recovery Procedures Reference Volume

•

VMS System Generation Utility Manual

Conventions
Convention

Meaning
In examples, a key name (usually abbreviated)
shown within a box indicates that you press a
key on the keyboard; in text, a key name is not
enclosed in a box. In this example, the key is
the RETURN key. (Note that the RETURN key is
not usually shown in syntax statements or in all
examples; however, assume that you must press
the RETURN key after entering a command or
responding to a prompt.)

xii

CTRL/C

A key combination, shown in uppercase with a
slash separating two key names, indicates that you
hold down the first key while you press the second
key. For example, the key combination CTRL/C
indicates that you hold down the key labeled CTRL
while you press the key labeled C. In examples, a
key combination is enclosed in a box.

$SHOW TIME
05-JUN-1988 11 :55:22

In examples, system output (what the system
displays) is shown in black. User input (what you
enter) is shown in red.

$ TYPE MYFILE.DAT

In examples, a vertical series of periods, or ellipsis,
means either that not all the data that the system
would display in response to a command is shown
or that not all the data a user would enter is
shown.

input-file, ...

In examples, a horizontal ellipsis indicates that
additional parameters, values, or other information
can be entered, that preceding items can be
repeated one or more times, or that optional
arguments in a statement have been omitted.

[logical-name]

Brackets indicate that the enclosed item is optional.
(Brackets are not, however, optional in the syntax
of a directory name in a file specification or in the
syntax of a substring specification in an assignment
statement.)

quotation marks
apostrophes

The term quotation marks is used to refer to
double quotation marks ("). The term apostrophe
( ') is used to refer to a single quotation mark.

Introduction to VAX Volume Shadowing

1 .1

Overview
Volume shadowing is a cooperative effort between the VMS operating system
and a Hierarchical Storage Controller (HSC) to record data on more than
one volume. This duplication of data provides greater data availability and
faster data accessibility. When data is recorded on more than one volume,
you have access to critical data even when one volume is unavailable. The
system can also find the data more quickly because it can search more than
one disk-it is as if there were additional read heads on a single disk drive.
(Note, however, that due to the multiple write operations, write performance
is slightly slower with volume shadowing.) In addition, when normal media
deterioration renders a volume unreadable, systems with volume shadowing
read the duplicate data and restore the data to the failed volume.
Volume shadowing allows you to unite compatible volumes into a shadow
set. A shadow set generally consists of two or more compatible disk volumes
(one is also allowed) referred to as shadow set members. After you create a
shadow set, most users and most software regard it as a single virtual unit. A
virtual unit is a software-created representation of a group of disks and disk
drives that compose a shadow set.
From the command level, you can use the VMS Mount Utility (MOUNT) to
create and add members to shadow sets, and the DCL commands SHOW
DEVICES and DISMOUNT to maintain them. In software programs you can
use the system service routines $MOUNT, $GETDVI, and $DISMOU to create
and maintain shadow sets. In DCL command procedures, the lexical function
F$GETDVI provides the same services as the $GETDVI system service.
You can mount shadow sets as private volumes or public volumes on systems
operating alone or in VAXclusters. The VMS operating system provides
volume shadowing for users of both Files-11 volumes and foreign volumes,
but many of the functions provided with Files-11 volumes must be user
supplied for foreign volumes.
To use VAX Volume Shadowing, you need a Hierarchical Storage Controller
(HSC) and DIGITAL Storage Architecture (DSA) disk volumes in addition to
one or more VAX processors.

1-1

Introduction to VAX Volume Shadowing
1.2 Volume Shadowing Terms

1 .2

Volume Shadowing Terms
Following are some important volume shadowing terms and their definitions.

1-2

$allocation-class$

$allocation-class$ is part of a naming convention for
virtual units and physical devices. This convention
is described in the VMS VAXcluster Manual. If your
system connects devices by dual paths to two HSCs,
you should specify those devices (and especially the
shadow set virtual units) using the allocation class
name $a/location-class$ instead of the HSC name
hsc$ (described in this section).

HSC

The Hierarchical Storage Controller (HSC) is a selfcontained, intelligent mass storage controller that
communicates with VAX processors to implement
volume shadowing on DIGIT AL Storage Architecture
(DSA) disks.

hsc$

hsc$ is part of a naming convention for virtual units
and physical devices. Because volume shadowing
requires an HSC, hsc$ replaces node$ for the node
name format described in the VMS VAXcluster
Manual. Physical devices (and the virtual unit that
represents them) connected to the same HSC all
use the same HSC name. For example, two devices
connected to the HSC named TROLL might be named
TROLL$DUA 1 and TROLL$DUA2.

Mount verification

Mount verification is a VMS feature that suspends 1/0
with volumes while they are changing status. Mount
verification also ensures that, following a suspension
in disk 1/0, the volume being accessed is the same as
was previously mounted. When volume shadowing is
installed, the mount verification feature also maintains
and validates shadow set membership for Files-11
shadow sets.

MSCP

Mass Storage Control Protocol (MSCP) is the
software protocol used to communicate between
VAX processors and HSCs.

Remote server

Remote servers implement the MSCP protocol. They
control disk operations separately from the host node
and then communicate information back to it. The
HSC is one example of a remote server.

Shadow set

A shadow set is one or more compatible physical disk
volumes connected together for volume shadowing
and represented by a virtual unit. Thus, the term
shadow set refers to the physical units and the virtual
unit.

Shadow set member

A shadow set member is a physical disk mounted
as part of a shadow set. Typically, all shadow set
members contain identical data in corresponding
logical blocks.

Introduction to VAX Volume Shadowing
1 .2 Volume Shadowing Terms

1 .3

Shadow set state change

A shadow set state change occurs when volumes
are added to or removed from a Files-11 shadow
set. During a shadow set state change, access to the
virtual unit is temporarily suspended. The shadow
set remains inaccessible until the host computer
or VAXcluster accepts a membership change. For
Files-11 volumes, mount verification controls this
acceptance.

Virtual unit

A virtual unit is a software-created representation of
a group of disks that compose a shadow set. Most
users and system resources communicate with the
virtual unit as if it were a physical device and disk
volume. The HSC then manages 1/0 to the physical
disks that are bound together as a shadow set.

Hardware Requirements
To use VAX Volume Shadowing, you need specific hardware in addition to
the VMS operating system. Following are the hardware requirements.
Processors and Controllers

VAX Volume Shadowing requires a minimum of one VAX processor, one
HSC intelligent mass storage controller, and two compatible disk drives
and volumes. 1 This configuration provides protection against either failure
of a single disk drive or deterioration of a single volume. Using two HSC
controllers provides a further guarantee of data availability in the event of
a single HSC failure. Using a VAXcluster and multiple HSCs provides the
greatest data availability.
When setting up a system or VAXcluster with volume shadowing, you should
do the following:
•

Connect all disk drives chosen for a shadow set to the same HSC
controller, if you are using single path connections.

•

Connect all disk drives chosen for a shadow set to the same pair of HSC
controllers, if you are using dual path connections.

•

Connect disk drives to different HSC I/O channels, when possible.

Compatible Disk Drives and Volumes

Volume shadowing requires compatibility among the physical units (disk
drives and volumes) that form a shadow set. For instance:

•

Units must have the same geometry, including the same number of
sectors per track, the same number of tracks per cylinder, and the same
number of cylinders per volume.

•

Units must have the same physical properties, including connections
conforming to those described previously for HSC connections.

•

Units must conform to the DIGITAL Storage Architecture (DSA), and
Mass Storage Controller Protocol (MSCP). They must replace bad blocks
without host intervention.

A shadow set can consist of only one disk, but this configuration cannot provide the desired duplicate data.

1-3

Introduction to VAX Volume Shadowing
1 .3 Hardware Requirements

•

Units should not have the hardware write-protection button pressed.
Hardware write protection stops volume shadowing software from
maintaining identical volumes.

For performance information related to system configurations, see Section 4.t
Figure 1-1 through Figure 1-3 show three possible system configurations for
volume shadowing. In addition to the hardware components, these figures
present how the virtual unit relates to the hardware.
Figure 1-1

Elements of a Shadow Set {One VAX -

One HSC)

hsc$ddcu:

Physical Device # 1

· hsc$ddcu:

Physical Device #2

hsc$ddcu:

Physical Device #3

ZK 4995 86

Figure 1-1 presents a system with one VAX processor and one HSC. In this
configuration, the devices and virtual unit use the hsc$ naming convention.

1-4

Introduction to VAX Volume Shadowing
1 .3 Hardware Requirements

Figure 1-2 presents a system with one VAX processor and three units
connected by dual paths to two HSCs. These devices and virtual unit all
use the same allocation class name.
Figure 1-2

Elements of a Shadow Set (One VAX -

Two HSCs)

ZK 499686

1-5

Introduction to VAX Volume Shadowing
1 .3 Hardware Requirements

Figure 1-3

Elements of a Shadow Set (A VAXcluster -

Two HSCs)

ZK-4994-86

Figure 1-3 presents a system with three VAX processors and three units
connected by dual paths to two HSCs. These devices and this virtual unit us
the same allocation class name.

1 .4

Mounting a Shadow Set
To mount a shadow set, you must perform the following steps:

1-6

Set up the VAX processors and HSC controllers to allow for the greatest
protection against hardware failure. See the VMS VAXcluster Manual for
details on VAXcluster configurations using multiple controllers.

Select compatible disk drive units and disk volumes properly ported
according to your system configuration. Also, make sure the hardware
write-protection buttons on the drives are in the out position (no write
protection).

Introduction to VAX Volume Shadowing
1 .4 Mounting a Shadow Set

Prepare the selected volumes for mounting. This includes physically
placing the volumes in the drives and allocating them (this is optional).
Then you must consider the data on the volumes you have chosen to
mount together, as follows:
•

If you intend to mount a new shadow set with volumes that contain
no useful data, you should initialize one volume. Initialize the
volume in the drive that you will list as the first shadow set member
in your mount operation. Give it a proper label that you will use for
the shadow set. The other volumes are initialized automatically when
they become shadow set members.

•

If you intend to mount a shadow set that includes a volume with
useful data, do not initialize the volumes.

Mount the shadow set using either the VMS Mount Utility or the
$MOUNT system service. You must be careful of the default copy
operations that overwrite data on shadow set members determined to be
less current than others.

The following example uses the MOUNT command to create a single shadow
set using RASO disks:
$ MOUNT /CONFIRM0 $2$DUS23:f)_$/SHADOW = ($2$DUA4: ,C) $2$DUA5: .8 $2$DUA7:8)_$ MYVOLUME0
DISK$MYVOLUME0

/CONFIRM is an optional qualifier that stops automatic copy operations
to disks determined to have the least correct data.

$2$DUS23 is the name of the virtual unit that represents the shadow set.

$2$DUA4, $2$DUA5, and $2$DUA7 are the physical units that are
shadow set members. Note that they must be the same device type.

MYVOLUME is the volume label of the shadow set virtual unit, and at
least one of 'the shadow set members.

DISK$MYVOLUME is the logical name of the shadow set virtual unit.

Chapter 2 describes more fully how to mount shadow sets using the Mount
Utility. See Chapter 3 for information about how to mount shadow sets with
the $MOUNT system service.

1.5

Shadow Set Changes
After a shadow set is mounted, volume shadowing must preserve the integrity
of the data written to it. When you first mount and initialize the shadow set,
each of the member volumes is identical and ready to receive identical data.
However, changes in the composition of the shadow set are inevitable,
because, for example:
•

Disk drives fail or need routine maintenance.

•

New disks are added to improve performance (or to replace other disks).

1-7

Introduction to VAX Volume Shadowing
1.5 Shadow Set Changes

Volume shadowing responds to shadow set composition changes by doing
the following:

1.6

•

Maintaining identical data on current shadow set members by
automatically detecting and replacing bad blocks on one shadow set
member and rewriting those bad blocks with good data from another
shadow set member.

•

Bringing newly mounted volumes up to full shadow set membership
through copy operations (see Section 2.1.4). Copying is automatic for
Files-11 shadow sets; you must specify the copy operations for foreign
shadow sets.

•

Notifying the system operator when a member is removed from a shadoV\
set.

Examining a Shadow Set
You can use the DCL command SHOW DEVICES, the system service
$GETDVI, and the corresponding lexical function F$GETDVI to get
information about a shadow set virtual unit and its corresponding physical
volumes. You might enter the DCL command SHOW DEVICES, as in the
following example:
$ SHOW DEVICES DUS1

Entering the virtual unit name DUSl as a parameter produces a display such
as the following:
Device
Name
$254$DUA39:
$254$DUA44:
$254$DUS1:

(HONOR)
(HONOR)
(HONOR)

Device
Status
ShadowSetMember
ShadowSetMember
Mounted

Error
Volume
Free Trans Mnt
Count
Label
Blocks Count Cnt
0 (member of $254$DUS1:)
0 (member of $254$DUS1:)
99268
81
1
0 SHD22AUG

In this display the HSC is named HONOR.
Or you might enter a command such as this:
$ SHOW DEVICES DJS

Entering a generic virtual unit name DJS as a parameter produces a display o
any virtual units representing shadow sets mounted on RA60 disks.
Device
Name
$254$DJS1:
$254$DJS2:

(HONOR)
(HONOR)

Device
Status
Mounted
Mounted

Error
Volume
Count
Label
0 LURK1$
0 LURKMASTER

Free Trans Mnt
Blocks Count Cnt
27060
35
7
85653
4 6

See Chapter 2 for a description of how to examine shadow sets using the
SHOW DEVICES command, and Chapter 3 for information about using
$GETDVI.

1-8

Introduction to VAX Volume Shadowing
1. 7 Adding and Removing Shadow Set Members

1 .7

Adding and Removing Shadow Set Members
After a shadow set is mounted, you can add physical units to it with the
VMS Mount Utility. You must use the same command syntax used to create
the shadow set, except you do not need to list the physical units currently
in the shadow set. Also, you do not need to add the /CLUSTER qualifier to
add the units clusterwide. The /CLUSTER qualifier is implied; a virtual unit
must represent the same shadow set members to every node on which it is
mounted.
In the following example, the first command creates the shadow set with
two shadow set members; the second command adds a third physical unit to
the same shadow set. Note that any data on the third volume is lost to an
automatic copy operation when the shadow set member is added.
$ MOUNT $6$DJS2: /SYSTEM /SHADOW=($6$DJA4:, $6$DJA5:) PHANTOMDISK DISK$PHANTOMDISK
$ MOUNT $6$DJS2: /SYSTEM /SHADOW=($6$DJA6:) PHANTOMDISK DISK$PHANTOMDISK

You can dismount shadow set virtual units and physical units with the DCL
command DISMOUNT or the $DISMOU system service. If you dismount
a virtual unit from one node, only the node from which you issued the
command dismounts the shadow set. (For details, see Section 2.4.) You
can dismount individual shadow set members directly as if they were not
members of a shadow set. Dismounting a shadow set member removes it
from the shadow set clusterwide; the membership of a shadow set must be
consistent to every node on which it is mounted.
For example, to remove a physical unit $5$DUA7 from a shadow set with the
three members $5$DUA4, $5$DUA7, and $5$DUA11, you might enter the
following command:
$ DISMOUNT $5$DUA7:

Note: If you attempt to dismount all the physical units in a shadow set, mount
verification requests that the operator restore a member to the shadow set.

1 .8

Dissolving a Shadow Set
You can dismount the virtual unit from one node in a VAXcluster and leave
the shadow set operational on the remaining nodes on which it is mounted. If
you dismount the virtual unit of a shadow set from all the VAXcluster nodes,
or from the only node with volume shadowing, you dissolve the shadow set.
After you dissolve a shadow set, each of the former shadow set members is
available for use. Each volume, however, continues to be marked as having
been part of a shadow set. Chapter 2 describes how to manage shadow sets,
including how to dissolve and re-create shadow sets to your advantage.

1-9

Introduction to VAX Volume Shadowing
1.9 Shadow Sets as System Disks and in VAXclusters

1 .9

Shadow Sets as System Disks and in VAXclusters
You can mount your system disk as a shadow set, but you must take
special steps when creating the shadow set. When you install VAX Volume
Shadowing in a VAXcluster, for example, you have to prepare each VAX
processor the same way. Volume shadowing adds complications to software
upgrade procedures on system disk shadow sets as well. Section 4.4 describE
how to prepare a system disk shadow set and boot from it. Section 4.5
describes the upgrade procedure.
Shadow sets mounted in a VAXcluster require special considerations.
Primarily, you should perform the volume shadowing procedures on each
VAXcluster node even if the shadow set is fully constructed on one node.
You should mount th·e shadow set exactly the same way on each node.
Mounting a shadow set clusterwide provides the following advantages:
•

The remote server informs each VAXcluster node of shadow set state
changes.

•

If an HSC fails in a VAXcluster with multiple HSCs, any VAXcluster nod

can switch the shadow set to an alternate HSC.
•

If the HSC fails in a VAXcluster with a single HSC, any VAXcluster nodE

can rebuild the shadow set when the HSC is available again.
Note that after you mount a shadow set clusterwide, you can dismount the
shadow set from one VAXcluster node and leave it operational on the other
cluster nodes.

Note: You cannot set up your quorum disk as a shadow set. A series of reques1
for the cluster quorum information would produce unpredictable results.

1-10

The Command-Level Interface

VAX Volume Shadowing provides enhancements to existing VMS utilities
and DCL commands that let you create, maintain, and dissolve shadow sets.
This chapter describes how to use the VMS Mount Utility, the VMS Backup
Utility, and the DCL commands SHOW DEVICES and DISMOUNT with
volume shadowing. The lexical function F$GETDVI is also described.

2.1

Creating a Shadow Set with the Mount Utility
You mount shadow sets with the Mount Utility using any valid MOUNT
qualifiers 1 , the name of the virtual unit, and the required /SHADOW
qualifier. You must name at least one physical device as a parameter to the
/SHADOW qualifier.
If you specify more than one physical device, more current Files-11 disks are
copied to less current Files-11 disks by default (see Section 2.1.4 for details).
To disable the copy operations, use the /NOCOPY qualifier. If you are
mounting a shadow set interactively, you can use the /CONFIRM qualifier,
which instructs MOUNT to display the targets of copy operations and request
permission before the copies are performed.
If you mount foreign volumes in a shadow set, to ensure identical data you
must use the appropriate copy-type specifier for each physical device named
(see Section 2.1.3 for details).
Restrictions

If the mount operation involves a copy operation, you must have override
volume protection (VOLPRO) privilege or your user identification code (UIC)
must match the owner UIC of the target volume.
Volume Shadowing Qualifier List

Following are the volume shadowing qualifiers and copy-type specifiers used
with the VMS Mount Utility.
Files-11 Volume Qualifiers

Defaults

/SHADOW=(physical-device-name[: ][, ... ])

None.

/[NO]CONFIRM

/NOCON FIRM

/[NO]COPY

/COPY

Foreign Volume Qualifier
/SHADOW=(copy-type=physical-device-name[: ][, ... ])

The /OVERRIDE=IDENTIFICATION and /NOMOUNT_VERIFICATION qualifiers are not recommended.

2-1

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

The following copy-type specifiers are used with the preceding foreign
volume qualifier.
Foreign Volume Copy-Type Specifiers
NQ_COPY=physical-device-name (default)
FULL _CQPY=physical-device-name
MERGE _COPY=physical-device-name

The following qualifier, used with MOUNT, lets you remount a former
shadow set member outside of a shadow set.

2.1.1

Qualifier

Default

/OVERRIDE=SHADQW_MEMBERSHIP

None.

Mounting a Files-11 Shadow Set
The format for mounting a Files-11 shadow set is as follows:
MOUNT virtual-unit-name[:]/SHADOW =
(physical-device-name[:][, . . . ])[, . . . ] [volume-label[, . . .

]] [logical-name[:]]

virtual-unit-name[:][, ... ]

The required name for the software representation of a shadow set. Use the
virtual unit naming formats [$allocation-class$]ddSu[:] or [hsc$]ddSu[:].
If the allocation class is not zero, use the allocation class format. If you
omit the HSC name or allocation class when you specify a virtual unit in a
VAXcluster, MOUNT substitutes the HSC name or allocation class of the mos
current shadow set member.

The dd describes the device type of the physical devices used. For example,
an RA60 disk drive is device type DJ, and an RASO or RA81 disk drive is
device type DU. You must match the code for a virtual device name with the
code for the type of physical devices proposed as shadow set members.
The S identifies the unit as a shadow set virtual unit.
The u is a unique number from 0 through 9999. This code is optional when
you create a shadow set. If you omit this code, the system provides a virtual
unit number. Numbering starts at 9999 and decrements to O; the first virtual
unit mounted is numbered 9999, the second 9998, and so forth.
If you are mounting a volume set of shadow sets and specify more than one
shadow set virtual unit, separate each with either commas or plus signs. The
shadow sets must be in the same volume set and the labels must be specifiec
in ascending order according to relative virtual unit number.

2-2

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

/SHADOW=(physical-device-name[:][, ... ])

The required volume shadowing qualifier that directs the Mount Utility to
bind the specified physical devices into a shadow set.
You must specify the name or names of the physical devices proposed as
shadow set member devices. If you specify only one device, you can omit the
parentheses.
physical-device-name[:][, ... ]

The name of a disk drive that contains a disk to be mounted in a shadow
set. Use the standard HSC-mounted device naming formats $allocationclass$ddcu[:] or hsc$ddcu[:). If your devices are dual ported to HSCs, use
the allocation-class format. For example, $125$DUA23 represents an RA80
or RA81 disk with unit number 23. The disk's allocation class is $125$. The
c part of the format is always A for HSC disks. An RA60 disk with unit
number 12 might be named TROLL$DJA12. The device is connected to an
HSC named TROLL. A named physical device becomes a shadow set member
represented by the virtual unit.
volume-label[, ... ]

Specifies the label for a virtual unit (each of the shadow set members takes
this label automatically). Labels can be from 1 to 12 characters. To add a
shadow set member to an existing shadow set, specify only the label of the
shadow set, not the label of the potential shadow set member.
If you do not specify a label, MOUNT selects the label for the shadow set
from the first shadow set member listed. Note also that, if proposed members
are not marked with shadow set information, MOUNT considers volumes
with labels that match the shadow set label more current than volumes
with labels that do not match. The less current volumes are targets of copy
operations.

Note: DIGITAL recommends you do not mount a shadow set with the
/OVERRIDE=IDENTIFICA TION qualifier; see Section 2.1.5.4 for details.
If you are mounting a volume set of shadow sets and specify more than
one volume label, separate the labels with either commas or plus signs. The
shadow sets must be in the same volume set and the labels must be specified
in ascending order according to relative virtual unit number.

logical-name[:]

Defines a 1- to 255-alphanumeric character string associated with the
mounted shadow set. Follow the same command syntax as you would to
mount any volume or volume set.
Note that most of the command format is the same as the format for
mounting Files-11 disks for individual use. For information about mounting
any disk, see the VMS System Services Reference Manual. The Guide to VMS
Files and Devices and the Guide to Maintaining a VMS System also explain how
to mount disks and disk sets.

2-3

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

2.1.2

MOUNT Examples
Example 1

This example forms the shadow set $45$DUS23, which includes shadow set
members $45$DUA4, $45$DUA5, and $45$DUA7.
$ MOUNT
$45$DUS23: /SHADOW= ( $45$DUA4:, $45$DUA5:, $45$DUA7:) _$ LURKINGVOL DISK$LURKINGVOL

Example 2

This example mounts a Files-11 volume set where each volume is a shadow
set.
$7$DUS23:0 /SHADOW= ($7$DUA4: ,fJ $7$DUA5:, $7$DUA7:), _$ $7$DUS24:0 /SHADOW = ($7$DUA9: ,fJ $7$DUA10:, $7$DUA12:), _$ $42$DUS26:0 /SHADOW= ($42$DUA20: ,f) $42$DUA21:, $42$DUA22:)
_$ LURKINGVOL1,8 LURKINGVOL2,8 LURKINGVOL38
DISK$LURKINGVOL0

$ MOUNT

These are the names of the virtual units that represent shadow sets
mounted in a volume set. Each set uses either RA80 or RA81 disks (not
mixed).

$7$DUA4, $7$DUA5, and $7$DUA7 ... $42$DUA22 are the physical
units that are shadow set members. Note that one of the shadow sets
uses disks from a different allocation class.

LURKINGVOLl, LURKINGVOL2, and LURKINGVOL3 are the volume
labels of the virtual units mounted in a Files-11 volume set.

G DISK$LURKINGVOL is the logical name that represents the volume set.

2.1.3

Mounting a Foreign Shadow Set
The format for mounting a foreign shadow set is as follows:
MOUNT /FOREIGN virtual-unit-name[:]/SHADOW =
(copy-type-specifier = physical-device-name[:][, . . .
[volume-label[, . . . ]] [logical-name[:]]

])

[, ...

Note: You cannot mount foreign shadow sets with the /CONFIRM and /COP)
qualifiers.
The format for foreign shadow sets is the same as for Files-11 shadow sets,
except for the addition of the copy-type-specifier. When you mount Files-1
volumes in a shadow set, MOUNT determines the correct copy operation to
ensure identical data on each disk. When you mount foreign volumes in a
shadow set, you must determine and specify the desired copy operation for
each disk. There are three copy-type specifiers: FULL_COPY, MERGE_
COPY, and NO_COPY. Note that MOUNT always uses the first shadow se
member listed as the source of copies to the other members. Thus, you mm
mount the first member with NO_COPY. You must determine the correct
copy operation for any other shadow set members. The default copy-type
specifier is NO_COPY.

2-4

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

FULL_CQPY
Instructs MOUNT to copy data from other shadow set members to the
specified volume. The specified volume should be a blank volume or a
former shadow set member that is not as current as the other shadow set
members.

MERGE_COPY
Instructs MOUNT to copy data from other shadow set members to the
specified volume and to copy data from the specified volume to other shadow
set members when the other shadow set members are unreadable. The
specified volume should be one whose data is considered as current or as
correct as any shadow set members, except for possible incomplete write
operations. The volume listed with this specifier becomes a source of data for
any volumes with unreadable blocks and is a target for data copying on all
other blocks.

NO_COPY
Instructs MOUNT to mount the specified volume as a shadow set member
with no copy operations. You must use this specifier with the first shadow set
member listed. If you list this specifier with any other volume, you should
know that the volume's contents are identical to all the current or potential
shadow set members. Note that NO_COPY is the default copy-type specifier.
If you mount foreign volumes with different data in a shadow set and do not
specify a copy operation for each disk, the shadow set members will not have
identical data. In this situation, a read request directed to the virtual unit
produces unpredictable data.
You must supply your own methods of marking volumes and determining
the correct copy operation for each shadow set member in a foreign shadow
set.
Example

This example shows a command string for mounting a foreign shadow set.
$ MOUNT/FOREIGN $213$DJS5:., /SHADOW = _$ (NO_COPY8 = $213$DJA2: ,EJ _$ FULL_COPY0 = $213$DJA10: ,f) _$ MERGE_COPY0 = $213$DJA20:f))

_, $213$DJS5 is the name of the virtual unit that represents a shadow set
consisting of RA60-type disks.
f)

$213$DJA2, $213$DJA10, and $213$DJA20 are the physical units that are
shadow set members.

NO_COPY is the specifier required to mount, with no copy operations,
the foreign disk $213$DJA2 in the shadow set.

FULL _COPY is the specifier required to mount, with a full copy
operation, the foreign disk $213$DJA10 in the shadow set.

MERGE_COPY is the specifier required to mount, with a merge copy
operation, the foreign disk $213$DJA20 in the shadow set.

2-5

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

2.1.4

Files-11 Copy Op.erations
Files-11 copy operations ensure that new shadow set members contain
data identical to other members. Volume shadowing software brings newly
mounted disks into full shadow set membership with full or merge copy
operations.
To perform a MOUNT operation that involves a copy operation, you must
have VOLPRO privilege or your user identification code (UIC) must match
the owner UIC of the target volume.

2.1.4.1

Full Copy
The full copy operation assumes that the newly added disk is less current
than, or unrelated to, the existing shadow set members. Data from the other
members is written to the new member to make it identical and thus a full
shadow set member. If you are re-creating a shadow set with former shadow
set members, the volumes most recently in the shadow set (or processed witr
BACKUP /IMAGE) are considered the sources for full copy operations. For
details, see Sections 2.7.3 and 2.8.

2.1.4.2

Merge Copy
The merge copy operation assumes that the newly added member differs
from the existing shadow set members, only as a result of an incomplete
write operation. Thus, the merge copy operation occurs only when a shadow
set is rebuilt due to an HSC failure.

During the updating process, the new disk is regarded as a source of data
when existing shadow set disks have unreadable data. If the merge copy
operation cannot read the newly added disk either, then it declares the block
in question to be identical on all shadow set members.

2.1.4.3

Determining the Correct Copy Operation
For Files-11 volumes, VAX Volume Shadowing performs the correct copy
operation automatically when you mount or add to a shadow set. MOUNT
interprets information recorded on current and potential shadow set volumes
to determine the correct copy operation for each volume. Each volume need~
either a full copy operation, a merge copy operation, or no copy operation.

Because every copy operation overwrites the data currently on the disk, you
should mount and add to shadow sets carefully. If you are not sure which
potential shadow set members are targets of copy operations, you can specif)
the /CONFIRM or /NOCOPY qualifier (see Sections 2.1.5.1 and 2.1.5.2 for
details).
MOUNT checks the following Files-11 volume information to determine the
correct copy operation.
Volume Label

MOUNT checks to see if the proposed shadow set disk volume label identifie
the volume as a former shadow set member or an unrelated volume. If the
volume labels are the same on volumes that have no volume shadowing
information on them, MOUNT uses the label of the volume listed as the first
shadow set member on the command line.

2-6

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

Proper Dismount

MOUNT checks to see if the proposed shadow set disk was correctly
dismounted, assuring that the volume contains no incomplete write
operations.
BACKUP Revision Number

A BACKUP /IMAGE restoration rearranges the location of data on a volume
and sets a revision number to record this change. MOUNT checks the
revision number of the proposed shadow set member against the numbers on
current or other proposed shadow set members.
Volume Shadowing Generation Number

When a volume joins a shadow set, it is marked with a volume shadowing
generation number. MOUNT checks this number on the newly mounted
volume against the generation numbers of current shadow set members.
The volume shadowing generation number is a record of shadow set
membership at a given time. Following the completion of each shadow
set membership change, MOUNT records a new number on each shadow
set member. This number is erased when you mount a former shadow set
member outside of the shadow set.
Example

In this example, $1$DUSO is the virtual unit name, $1$DUA10 and
$1$DUA1 l are the names of the shadow set members, and HSCOOl (with
allocation class name $1$) is the name of the HSC to which the disk drives
are connected.
$MOUNT $1$DUSO: /SHADOW=($1$DUA10: ,$1$DUA11:) SHADOWDISK
%MOUNT-I-MOUNTED, SHADOWDISK
mounted on _$1$DUSO: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA10: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMCOPY, _$1$DUA11: (HSC001) added to the shadow set
with a copy operation

This example shows how to create a shadow set where the software
determines automatically the correct copy operation for the two shadow
set members. MOUNT checks the volume shadowing generation numbers on
the volumes, selects the most current shadow set member, and performs the
appropriate copy operation. In this example, $1$DUA10 is the most current
volume and is the source of the copy operation to $1$DUA11.

2.1.5

Qualifiers
You must use the /SHADOW qualifier when mounting all shadow sets. For
Files-11 shadow sets, /COPY and /NOCONFIRM are the default qualifiers.
Copying proceeds automatically using data on the shadow set members to
determine the correct copy operation. If you are not sure of the contents of
the specified shadow set members, you can specify either the /NOCOPY or
the /CONFIRM qualifier in your Files-11 MOUNT command string.

2-7

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

2.1.5.1

The /CONFIRM Qualifier (Files-11 Shadow Sets)
The /CONFIRM qualifier controls whether the Mount Utility (MOUNT)
issues a request to confirm a full copy operation when mounting a shadow
set. The default is /NOCONFIRM. The format for mounting a shadow set
with the /CONFIRM qualifier is as follows:

MOUNT /[NO]CONFIRM virtual-unit-name[:] /SHADOW=(physical-device-name[:][, . . . ])
[, . . .

]

[volume-label[, . . .

]

[logical-name[:]]

You can specify /CONFIRM as a precaution to avoid erasing important data
during copy operations. /CONFIRM stops automatic copying of targeted
potential shadow set members. When you mount or add to a shadow set,
members that contain data less current than other shadow set members
are targets for full copy operations. Unless you specify the /CONFIRM or
the /NOCOPY qualifier, MOUNT automatically overwrites the data of the
targeted volumes.
MOUNT /CONFIRM displays the volume label and volume owner for any
specified physical device that requires a full copy operation. MOUNT then
stops and displays the following prompt:
Allow FULL shadow copy on the above member(s)? [NJ:

If the targets of copy operations are as expected, type YES, and the MOUNT
command proceeds automatically with full copy operations allowed. If not,
type NO, press RETURN, or press CTRL/Z. The command quits without
mounting any new shadow set members, including those that do not require
a full copy operation. If you type a response other than these, the prompt is
redisplayed. You can use any combination of upper- and lowercase letters,
and abbreviate to one or more letters.

Section 2.1.4.3 describes how MOUNT determines the sources and targets
of shadow set copy operations. In brief, the shadow set member with the
most current volume shadowing generation number is the source for copy
operations to potential shadow set members. Other potential shadow set
members must have been marked with identical generation numbers or they
are targets for full copy operations.
The /CONFIRM qualifier is similar to the /NOCOPY qualifier except that
with /NOCOPY there is no interactive exchange. /NOCOPY also terminates
the mount operation if there are any potential full copy operations. Use
/CONFIRM to mount a shadow set interactively, and use /NOCOPY
to mount shadow sets in the site-specific startup command procedure
SYS$MANAGER:SYSTARTUP.COM. (See the /NOCOPY qualifier for
information about using it with a system disk shadow set.)
Example 1

This example shows how to use the /CONFIRM qualifier to check the status
of potential shadow set members before any data is erased.
$ MOUNT/CONFIRM DUS23: /SHADOW=($1$DUA4: ,$1$DUA6:) SHADOWVOL0
%MOUNT-F-SHDWCOPYREQ, shadow copy required
Virtual Unit - $1$DUS23 (HSC001)
Volume Label - SHADOWVOLf)
Member
Volume Label Owner UICC)
$1$DUA6: (LOVE)
SCRATCH
[100,100J
Allow FULL shadow copy on the above member(s)? [NJ: NOC»
$

2-8

This command instructs MOUNT to build a shadow set, with the specified
devices, and prompt for permission to perform any full copy operations.

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

Because a full copy operation is necessary, the virtual unit name and the
volume label are displayed.

The display also includes the physical device name, the volume label, and
the volume owner of the potential shadow set member that requires the
copy operation.

A response of NO instructs MOUNT to quit with no mounting or
copying.

Example 2
This example shows how to use the /CONFIRM qualifier to check the status
of potential shadow set members before any data is erased. This time a
response of YES to the prompt instructs MOUNT to form the shadow set
with a full copy operation.
$MOUNT/CONFIRM DUS23: /SHADOW=($1$DUA4: ,$1$DUA6:) SHADOWVOL
%MOUNT-F-SHDWCOPYREQ, shadow copy required
Virtual Unit - $1$DUS23 (HSC001)
Volume Label - SHADOWVOL
Member
Volume Label Owner UIC
$1$DUA6: (LOVE)
SCRATCH
[100,100]
Allow FULL shadow copy on the above member(s)? [NJ: YES
%MOUNT-I-SHDWMEMSUCC, _$1$DUA4: (HSC001) is now a valid member of the
shadow set
%MOUNT-I-SHDWMEMCOPY, _$1$DUA6: (HSC001) added to the shadow set with
a copy operation
$

2.1.5.2

The /COPY Qualifier (Files-11 Shadow Sets)
The /COPY qualifier enables or disables copy operations on physical devices
you name when mounting or adding to a shadow set. The default is /COPY.
Section 2.1.4.3 describes how MOUNT determines the sources and targets
of shadow set copy operations. Following is the format for the /COPY
qualifier:

MOUNT /[NO]COPY virtual-unit-name[:] /SHADOW=(physical-device-name[:][, . . .
[, . . . ] [volume-label[, . . . ] [logical-name[:]]

])

You can specify /NOCOPY as a precaution to avoid erasing important data
during copy operations. /NOCOPY stops automatic copying of targeted
potential shadow set members. When you mount or add to a shadow set,
members that contain data less current than other shadow set members
are targets for full copy operations. Unless you specify the /NOCOPY or
the /CONFIRM qualifier, MOUNT automatically overwrites the data of the
targeted volumes.
A MOUNT /NOCOPY operation fails if any of the specified potential shadow
set members require full copy operations. Error messages identify the targets
of full copy operations. If the targets are as expected, you can mount the
shadow set with the /COPY qualifier. If not, you have not lost data and can
enter a new command that specifies units that can be overwritten.
The /NOCOPY qualifier is similar to the /CONFIRM qualifier except that
with /CONFIRM there is an interactive exchange in which you can continue
a mount with copy operations. Use /CONFIRM to mount a shadow set
interactively, and /NOCOPY to mount shadow sets in the site-specific
startup command procedure SYS$MANAGER:SYSTARTUP.COM. (Using the
/NOCOPY qualifier with a system disk shadow set either has no effect, as

2-9

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

in the case where the system boots from a virtual unit, or causes the mount
operation to fail, which is not generally useful for a system disk.)
The /NOCOPY qualifier guards against accidental destruction of data when
the system reboots and forms a shadow set using incorrect volumes (caused
by different volumes being put into the drives, or drive unit plugs being
accidentally switched while the system is down).

Example
This example shows how to use the /NOCOPY qualifier to check the status
of potential shadow set members before any data is erased.
$ MOUNT/NOCOPY DUS2: /SHADOW=($1$DUA4: ,$1$DUA6: ,$1$DUA7:) _$ SHADOWVOL DISK$SHADOWVOIA)
%MOUNT-F-SHDWCOPYREQ, shadow copy required
%MOUNT-I-SHDWMEMFAIL, DUA7: failed as a member of the shadow set
%MOUNT-F-SHDWCOPYREQ, shadow copy required@
$ MOUNT/COPY DUS2: /SHADOW=($1$DUA4: ,$1$DUA6: ,$1$DUA7:) _$ SHADOWVOL DISK$SHADOWVOLC)
%MOUNT-I-MOUNTED, SHADOWVOL
mounted on _$1$DUS2: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA4: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMSUCC, _$1$DUA6: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMCOPY, _$1$DUA7: (HSC001) added to the shadow set
with a copy operationG

This command instructs MOUNT to build a shadow set with the specifiec
devices, but only if no copy operations are required.

MOUNT did not build the shadow set because the specified disk, loaded
on device $1$DUA7, was a target for a full copy operation. At this point
you can verify that the volume in device $1$DUA7 does not contain any
useful data. You can then proceed using the /COPY qualifier.

This command instructs MOUNT to build a shadow set providing the
necessary copy operations.

G The shadow set is mounted. The volume in device $1$DUA7 receives a
full copy operation.

2.1.5.3

The /OVERRIDE=SHADQW_MEMBERSHIP Qualifier
The SHADOW_MEMBERSHIP option of the /OVERRIDE=option qualifier
of the MOUNT command lets you remount former shadow set members for
write operations outside of the shadow set. Use the following format:
MOUNT /OVERRIDE=SHADOW_MEMBERSHIP
[volume-label[, . . .

physical-device-name[:][, ...

]] [logical-name[:]]

When you attempt to mount a former shadow set member outside of a
shadow set, MOUNT automatically mounts the volume write-locked to
prevent accidental alteration of data. To mount a former shadow set
member for write operations, you must specify /OVERRIDE=SHADOW_
MEMBERSHIP.

Note: When you use this qualifier, the shadow set generation number is erased
from the volume. If you then remount the volume in the former shadow
set, MOUNT considers it an unrelated volume and marks it for a full cop:
operation.

2-10

The Command-Level Interface
2.1 Creating a Shadow Set with the Mount Utility

To use /OVERRIDE=SHADOW_MEMBERSHIP you must have VOLPRO
privilege or your UIC must match the owner UIC of the volume. See the
VMS Mount Utility Manual for a description of the /OVERRIDE=option
qualifier.
Example

This example shows how to override the write protection and erase the
volume shadowing generation number field, thus mounting a former shadow
set member on $4$DUA20.
$ MOUNT/OVERRIDE=SHADOW_MEMBERSHIP $4$DUA20: WORKDISK

2.1.5.4

Using MOUNT/OVERRIDE=IDENTIFICATION
Although any valid MOUNT qualifier is allowed, DIGITAL does not
recommend using /OVERRIDE=IDENTIFICATION. If you mount a shadow
set with this qualifier and individual shadow set members start with different
volume labels, you can lose data. MOUNT automatically selects the label
for the shadow set from the first shadow set member listed. For example, if
you mount a shadow set with the /OVERRIDE=IDENTIFICATION qualifier
and the first member listed is labeled SCRATCH (contains no useful data),
SCRATCH becomes the label for the shadow set regardless of the labels and
data on the other volumes. MOUNT considers shadow set members with
labels that match the shadow set label more current than those with labels
that do not match. Thus, the member labeled SCRATCH becomes the source
of full copy operations to the other members whether or not it contains the
most correct data.

2.1.5.5

Using MOUNT/NOMOUNT_VERIFICATION
Mount verification maintains and validates shadow set membership in
Files-11 shadow sets. To avoid disabling important volume shadowing
functions, do not mount a Files-11 shadow set with the /NOMOUNT_
VERIFICATION qualifier.
If you specify the /NOMOUNT_VERIFICATION qualifier, the shadow set
becomes unusable at the first shadow set state change.

2.2

Adding Members to a Shadow Set
Use the VMS Mount Utility to add physical units to a shadow set. For
Files-11 volumes, use the same syntax as you used to create the shadow set
except specify only the device names of the devices you intend to add; you
do not need to specify all the current members of the shadow set. You can
specify current members without changing their membership state.
For foreign volumes, you must specify the device names of the units you
want to add and the type of copy operation needed to make the data on each
shadow set member identical.
You must mount every member of the shadow set exactly the same way.
This means any MOUNT qualifiers specified at the time of shadow set
creation override any MOUNT qualifiers you specify when you add a
shadow set member. Also, when,you add volumes to an existing shadow
set mounted across a VAXcluster, shadowing software automatically adds the
new members on each VAXcluster node.

2-11

The Command-Level Interface
2.2 Adding Members to a Shadow Set

Example

This example shows two commands. The first command creates the Files-11
shadow set with two members; the next adds a volume to the same shadow
set.
$ MOUNT/SYSTEM $3$DJS4: /SHADOW = ($3$DJA7:, $3$DJA8:)
FORMERSELF
%MOUNT-I-MOUNTED, FORMERSELF
mounted on _$3$DJS4: (HSC003)
%MOUNT-I-SHDWMEMSUCC, _$3$DJA7: (HSC003) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMSUCC, _$3$DJA8: (HSC003) is now a valid member of
the shadow set
$ MOUNT/SYSTEM $3$DJS4: /SHADOW = $3$DJA6: FORMERSELF
%MOUNT-I-SHDWMEMCOPY, _$3$DJA6: (HSC003) added to the shadow set
with a copy operation

The disks $3$DJA6 and $3$DJA10 are mounted as system volumes in the
shadow set identified by virtual unit $3$DJS4. The shadow set now include~
three shadow set members: $3$DJA6, $3$DJA7, and $3$DJA8. In this
example, when you add $3$DJA6 after the shadow set already exists, the
added volume receives full copy operations.
Section 2.8 describes how to maintain a shadow set with controlled adding c
shadow set members.

2.3

Removing Members from a Shadow Set
Use the DCL command DISMOUNT to remove a shadow set member from
a shadow set. Specify the physical device directly, just as you specify any
device for dismounting. See the VMS DCL Dictionary for a description of thE
DISMOUNT command.
The format for dismounting a shadow set member is as follows:
DISMOUNT physical-device-name[:]

The physical-device-name specifies the name of the shadow set member
to be dismounted. Use the standard HSC-mounted device naming formats
$allocation-class$ddcu[:] or hsc$ddcu[:]. If your devices are dual ported to
HSCs, use the allocation-class format. For example, $125$DUA23 represent
an RASO or RA81 disk with unit number 23. The disk's allocation class is
$125$. The c part of the format is always A for HSC disks. GRUFF$DJA12
represents an RA60 disk with unit number 12. The device is connected to a
HSC named GRUFF.
Although you dismount a shadow set member with standard DISMOUNT
command syntax, the command produces the following behavior specific to
volume shadowing:

2-12

•

Because you must dismount the shadow set member from each
VAXcluster node, the /CLUSTER qualifier is assumed automatically.

•

When you dismount a volume from a shadow set, you produce a situafo
similar to a hardware disk failure. The entire shadow set enters a shade
set state change under mount verification. This suspends I/O until ead
node accepts the new composition of the shadow set.

The Command-Level Interface
2.3 Removing Members from a Shadow Set

•

Volumes are marked as not being properly dismounted (as they would be
in the event of a hardware disk failure) due to the possibility of opened
files or incomplete I/O operations. Thus, the volume is considered less
current than other remaining shadow set members.

•

After removal, shadow set members remain marked as having been
members of a shadow set. This mark aids in determining the correct
copy operation if you remount the volume in a Files-11 shadow set. A
dismounted former shadow set member is automatically mounted writelocked if someone accidentally mounts it outside of a shadow set. To
remount a former shadow set member outside of a shadow set, you must
mount it with the /OVERRIDE=SHADOW_MEMBERSHIP qualifier.

•

After every membership change in a Files-11 shadow set, the remaining
shadow set members are marked with a number that identifies them as
being more current than former shadow set members. This mark aids in
determining the correct copy operation if you remount the volume in a
Files-11 shadow set.

•

You cannot dismount a shadow set member that is undergoing a copy
operation. If you attempt such a dismount, you receive the following
error message:
%SYSTEM-F-DEVACTIVE,

device is active.

You must wait until the copy operation is complete before you dismount
the shadow set member. You can, however, abnormally terminate the
copy operation if you dismount the entire shadow set.
•

2.4

If you attempt to dismount all the physical units in a shadow set, mount
verification sends a request to the operator to restore the last known valid
member to the shadow set.

Dismounting and Dissolving a Shadow Set
Use the DCL command DISMOUNT to dismount shadow sets. In place of
the device-name parameter, you specify the shadow set virtual unit name. If
your shadow set is mounted on one node, a DISMOUNT command dissolves
it; if your shadow set is mounted on several nodes in a VAXcluster, you can
dismount the shadow set from each node separately. To dissolve a shadow
set in a VAXcluster, you must specify the /CLUSTER qualifier or dismount
the shadow set from every node. After a shadow set is dissolved, you can use
the former members individually.

t',:.·" . .
~~.ft~;
~~·

The format for dismounting or dissolving a shadow set is as follows:
DISMOUNT virtual-unit-name[:]

Dismounting a virtual unit is similar to dismounting a regular Files-11
physical unit. See the VMS DCL Dictionary for information about using
DISMOUNT. If you specify /UNLOAD, the shadow set members are spun
down after the shadow set is dissolved.
You might enter the following command to dissolve a shadow set:
$DISMOUNT/CLUSTER $12$DJS9998:

This command dismounts the shadow set represented by the virtual unit
$12$DJS9998, from every VAXcluster node.

2-13

The Command-Level Interface
2.4 Dismounting and Dissolving a Shadow Set

After you dissolve a shadow set, the volumes continue to be marked as being
former shadow set members. Section 2.8 discusses some issues to consider
when you remount former shadow set members.

2.5

Examining a Shadow Set with the DCL Com~and SHOW DEVICES
This section describes how to use SHOW DEVICES to examine volume
shadowing virtual units and shadow set members. See the VMS DCL
Dictionary for a full description of how to use the SHOW DEVICES command.
You can use any of the SHOW DEVICES qualifiers when you examine virtual
units or shadow set members.

2.5.1

Listing Shadow Set Virtual Units
Use SHOW DEVICES in the following format to display information about
virtual uni ts:
SHOW DEVICES [virtual-unit-name[:]]

The virtual-unit-name replaces device-name as the SHOW DEVICES
command parameter for virtual units. Use the virtual-unit-name format
ddSu, Hsc$ddSu, or $allocation-class$ddSu.
The format for SHOW DEVICES changes only in the format for the virtual
· unit name. As with any SHOW DEVICES command, the colon is optional.
Note also that you can specify a complete virtual unit name (or a portion
of a virtual unit name) just as you can with device names. If you omit the
virtual unit number, SHOW DEVICES lists all the shadow set virtual units
representing shadow set member disks of the type specified. If you truncate
a device name (for example, you specify D), SHOW DEVICES lists all the
devices and all the virtual units that begin with the letter or letters you
entered (in this case, D).
When you specify the virtual unit number, SHOW DEVICES displays the
names of the shadow set members it represents. If you use the /FULL
qualifier, SHOW DEVICES displays full information about the virtual unit
and all the associated shadow set members.
Because. i~dividual shadow set members are not ~P?~~.-%d. .~
...l'.?~'9.:~.--. ··.:~. e9. .· i.n
the traditional sense, a SHOW DEVICES comma ·· ·~~i:f:~~]::C:)Jf:kJ~D or
/MOUNTED displays only virtual units.
,;;",; ..;t'::·;;.-,t:(€::'::~:~./.;:~;,;,:~~f

2.5.2

Listing Shadow Set Members

~~~;~~~~'.l~~1t~

Use the same format fo.r the SHOW J?EVICE? co_~~'-:
members as you use with other physical devices.'."'''
shadow set members of the device name you spe
Because shadow set members are not mounted in
all have the same device characteristics, SHOW D_
relevant data with the associated virtual unit. Lis ·
include information about current copy operation·
shadow set members are not allocated or mounte
a SHOW DEVICES command with /ALLOCATE,:
only virtual units.

2-14

r~~1\··:,. ~:~J,!-~~; set

~I1fajiq·:·JJ$~~'.·~:jill

.··:~}.~'::::·:::ff_~:f;;~~/~-~

~~< :.~-"'-':.~:.:~k"' ~~ <. ... ·.~1~~l·

... ··

~;aitd th~

·of tl
mbe
idual

The Command-Level Interface
2.5 Examining a Shadow Set with the DCL Command SHOW DEVICES

2.5.3

SHOW DEVICES Examples
Example 1

In this example the shadow set identified by the virtual unit DUSI includes
two shadow set members, $254$DUA39 and $254$DUA44, as well as the
virtual unit $254$DUS1. The listings for shadow set members do not include
volume labels and other information, because the members are not mounted
in the traditional sense.
$ SHOW DEVICES DUS1:
Device
Name
$254$DUA39:
$254$DUA44:
$254$DUS1:

(HONOR)
(HONOR)
(HONOR)

Device
Status
ShadowSetMember
ShadowSetMember
Mounted

Error
Count
4
4
0

Volume
Free Trans Mnt
Label
Blocks Count Cnt
(member of $254$DUS1:)
(member of $254$DUS1:)
SHD22JUN
99268
81
1

Example 2

This example shows how the /FULL qualifier produces a display with more
information.
$ SHOW DEVICES/FULL DUS
Disk $254$DUS1: (HONOR), device type RA80, is online, mounted, file-oriented
device, shareable, available to cluster, shadow set virtual unit, error
logging is enabled.
Error count
Owner process
Owner process ID
Reference count
Total blocks
Total cylinders
Host name
Allocation class
Volume label
Cluster size
Free blocks
Extend quantity
Mount status
Extent cache size
File ID cache size
Quota cache size

00000000
42
237212
274
"HONOR"
254
"SHD22JUN"
1

99268
5

System
64
64
0

Operations completed
23517
Owner UIC
[1, 1]
Dev Prot
S:RWED,O:RWED,G:RWED,W:RWED
Default buffer size
512
Sectors per track
31
Tracks per cylinder
28
Host type, available
HS50, yes

o.
Relative volume number
Transaction count
81
Maximum files allowed
59303
Mount count
1
Cache name
"_$254$DUS1:XQPCACHE"
Maximum blocks in extent cache
9926
Blocks currently in extent cache
9383
Maximum buffers in FCP cache
508

Volume status: subject to mount verification, file high-water marking, writethrough caching enabled.
Members of shadow set $254$DUS1: are $254$DUA39:, $254$DUA44:.
Disk $254$DUS28: (SHEMP), device type RA81, is online, mounted, file-oriented
device, shareable, available to cluster, shadow set virtual unit, error
logging is enabled.

2-15

The Command-Level Interface
2.5 Examining a Shadow Set with the DCL Command SHOW DEVICES

Error count
Owner process
Owner process ID
Reference count
Total blocks
Total cylinders
Host name
Allocation class

0
1111

00000000
1
891072
1248
"SHEMP"
254

Volume label
"CASPER28JUL"
1
Cluster size
Free blocks
885302
Extend quantity
5
Mount status
System
Extent cache size
64
File ID cache size
64
0
Quota cache size

Operations completed
223
[DEVO,SYSTEMGURU]
Owner UIC
S:RW,O:RWED,G:R,W:R
Dev Prot
Def a ult buff er size
512
Sectors per track
51
Tracks per cylinder
14
Host type, available
HS50, yes
Relative volume number
0
Transaction count
1
Maximum files allowed
222768
Mount count
4
"_$254$DUS1:XQPCACHE"
Cache name
Maximum blocks in extent cache
88530
Blocks currently in extent cache
0
Maximum buffers in FCP cache
508

Volume status: write-through caching enabled.
Volume is also mounted on LARRY, MOE, CURLEY.
Members of shadow set $254$DUS28: are $254$DUA52:, $254$DUA119:.

Example 3

This example shows how truncating the device name to D causes information
about all devices and virtual units that begin with the letter D to be displayed.
$ SHOW DEVICES D
Device
Name
$7$DLAO:
$7$DMAO:
$7$DMA1:
$7$DRA2:
$7$DRA5:
$7$DRB6:
$7$DRB7:
$7$DYAO:
$7$DYA1:
$254$DJA1:
$254$DJA2:
$254$DJA38:
$254$DJA149:
$254$DUAO:
$254$DUA5:
$254$DUA39:
$254$DUA44:
$254$DUA52:
$254$DUA101:
$254$DUA102:
$254$DUA103:
$254$DUA119:
$254$DUA129:
$254$DUS1:
$254$DUS28:

(LARRY)
(LARRY)
(LARRY)
(MOE)
(MOE)
(LARRY)
(LARRY)
(LARRY)
(LARRY)
(LOVE)
(LOVE)
(LOVE)
(LOVE)
(LOVE)
(LOVE)
(LOVE)
(LOVE)
(HONOR)
(LOVE)
(LOVE)
(LOVE)
(HONOR)
(LOVE)
(LOVE)
(HONOR)

Device
Status
Online
Online
Mounted
Online
Online
Mounted
Mounted
Online
Online
Mounted
Mounted
Mounted
Online
Mounted
Mounted wrtlck
ShadowSetMember
ShadowSetMember
ShadowSetMember
Mounted
Mounted
Mounted
ShadowCopying
Mounted wrtlck
Mounted
Mounted

2-16

Error
Count
0
0
0
0
0
0
0
10
10
0
0
0
1
0
0
4
4
8
0
0
0
0
0
0
0

Volume
Label
DGR_D$

Free Trans Mnt
Blocks Count Cnt
4266

CLUSTERDUMP1
CLUSTERDUMP2

694938
616281

1
1

4
4

FOLKD$_I
PAGED$_I
REGFACBLD

52863
486
313587

31
3
1

5
4
4

VMS22MAY
481043
1
124176
1
RES22JUL
(member of $254$DUS1:)
(member of $254$PUS1:)
(member of $254$DUS28:)
2
WORK12$
302034
WORK13$
395910
3
WORK14$
541047
1
(being added to $254$DUS28 : ) 0
1
RES02JUL
133810
SHD22JUL
99303
82
CASPER28JUN
888919
1

5
4

4
4
4
4
1
4

Device $254$DUA119 is being added to the shadow set represented by
$254$DUS28. The addition of this device requires a copy operation.

The Command-Level Interface
2.6 Using the F$GETDVI Lexical Function

2.6

Using the F$GETDVI Lexical Function
The F$GETDVI lexical function provides another method for obtaining
information about shadow sets. Through the use of the shadow set item
arguments, you can determine the following types of information:
•

Whether a device is a shadow set virtual unit or a shadow set member

•

Whether a copy operation is in progress on a device

•

What type of copy operation is in progress on a device

•

The name of the virtual unit that represents the shadow set of which the
particular device is a member

•

The entire membership of a shadow set, including the virtual unit and all
of the members

•

Whether or not a member has been removed from the shadow set by the
remote server

The format for the F$GETDVI lexical function is as follows:
F$GETDVl(device-name,item)

The F$GETDVI function returns information about all items that you can
specify with the $GETDVI system service. Table 2-1 lists the volume
shadowing items you can specify with the F$GETDVI function, the type
of information returned, and the data types of the return values.
See the VMS DCL Dictionary for additional information about the F$GETDVI
lexical function. For information about the $GETDVI system service, see the
VMS System Services Reference Manual; for information on using $GETDVI
with volume shadowing, see Section 3.3.
Table 2-1

F$GETDVI Items for Volume Shadowing

Item

Information Returned

SHOW_CATCHUP_
COPYING

Returns the string "TRUE" or "FALSE" to indicate
whether the device is a member that is receiving a
full copy operation before joining a shadow set.

SHDW _FAILED_MEMBER

Returns the string "TRUE" or "FALSE" to indicate
whether the device is a member that has been
removed from the shadow set by the remote
server.

SHOW_MASTER

Returns the string "TRUE" or "FALSE" to indicate
whether the device is a virtual unit.

SHOW_MASTER_NAME

Returns as a string the device name of the virtual
unit that represents the shadow set of which
the specified device is a member. F$GETDVI
returns a null string if the specified device is not
a member, or is, itself, a virtual unit. The device
name includes the allocation class if the allocation
class is not zero; otherwise it includes the HSC
name.

2-17

The Command-Level Interface
2.6 Using the F$GETDVI Lexical Function

Table 2-1 (Cont.)

F$GETDVI Items for Volume Shadowing

Item

Information Returned

SHDW_MEMBER

Returns the string "TRUE" or "FALSE" to indicate
whether the device is a shadow set member.

SHDW_MERGE_COPYING

Returns the string "TRUE" or "FALSE" to indicate
whether the device is a member that is receiving c
merge copy operation before joining a shadow set

SHDW_NEXT_MBR_NAME

Returns as a string the device name of the next
member in the shadow set. If you specify a
virtual unit, F$GETDVI returns the device name of
the lowest-numbered member. If you specify a
member, F$GETDVI returns the device name of
the member with the next highest number. If you
specify the device name of the highest-numbered
member, F$GETDVI returns a null string. If you
specify the name of a device that is neither a
virtual unit nor a member, F$GETDVI returns a nul
string.
F$GETDVI returns the device name of the next
member in the shadow set even if the next
member has been removed from the shadow
set by the remote server.
The device name includes the allocation class if th
allocation class is not zero; otherwise it includes
the HSC name.

Example
To check a device for possible shadow set membership, you might include
the following DCL command in a command procedure.
$IF F$GETDVI( 11 WRKD$: 11 , 11 SHDW_MEMBER 11 ) THEN GOTO SHADOW_MEMBER

If WRKD$ (a logical name for a disk) is a shadow set member, then
F$GETDVI returns "TRUE" and directs the procedure to the label SHADOW
MEMBER.

2. 7

Performing Backup Operations on a Shadow Set
The following subsections describe several approaches to shadow set backuf
operations. Standalone BACKUP restrictions are discussed in Section 4.7.

2.7.1

Using a Shadow Set Copy as a Backup
You can add a disk to an existing shadow set to produce a copy of the data
on the shadow set. If you then dismount the shadow set, the disk is identic'
to the other disks of the former shadow set (see the following example). Thi
is the recommended method for producing an identical copy of a shadow se
If you must maintain the shadow set on line, you can dismount the membe1
without dismounting the shadow set. However, this marks the volume as
not being properly dismounted due to the possibility of opened files and
incomplete I/O operations.

2-18

The Command-Level Interface
2.7 Performing Backup Operations on a Shadow Set

Example

This example shows how to use volume shadowing copy operations to create
an offline identical. disk volume you can then use as a backup of your shadow
set.
$MOUNT/SYSTEM DUSO:/SHADOW=$1$DUA10: SHADOWFACTS
%MOUNT-I-MOUNTED, SHADOWFACTS mounted on _$1$DUSO: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA10: (HSC001) is now a valid member of
the shadow set

This command creates a shadow set with one shadow set member.
$MOUNT/SYSTEM DUSO:/SHADOW=$1$DUA11: SHADOWFACTS
%MOUNT-I-SHDWMEMCOPY, _$1$DUA11: (HSC001) added to the shadow set with
a copy operation

This command adds a second member, $1$DUA11, to the shadow set. At this
point you must wait for the copy operation to complete before dismounting
the shadow set. When the copy is completed, messages are sent to the system
console and any operators enabled to receive them.
$DISMOUNT $1$DUSO:

This command dismounts the shadow set leaving $1$DUA10 and $1$DUA11
with logically identical volumes. At this point you can re-create the shadow
set with one of the volumes and keep the other as a backup.

2.7.2

Using the VMS Backup Utility
Generally you can use the VMS Backup Utility (BACKUP) with shadow sets
as you do with regular volumes. (See the VMS Backup Utility Manual for a
description of how to back up volumes.) You can create BACKUP save sets or
copies from shadow sets by using the shadow set virtual unit name instead of
a physical device name as the input specifier. However, you cannot always
restore to a shadow set by listing the virtual unit name as an output specifier.
The main restriction is to any backup restoration that requires you to mount
the target volume with the /FOREIGN qualifier. If you mount your Files-11
shadow set as a foreign shadow set, you lose the automatic copy operations
and error recovery normally provided. The proper procedure for a BACKUP
/IMAGE restoration is described in Section 2.7.3.

Note: Standalone BACKUP is incompatible with shadow sets. See Section 4.7
for details.
The format for a BACKUP operation on a shadow set is as follows:
BACKUP input-specifier output-specifier

The format is the same as for any BACKUP operation.
The following command, for example, designates a virtual unit for the input
specifier:
$ BACKUP /RECORD

$7$DUS2: [ * . . .

] /SINCE= BACKUP

MTAO: 230CT. BCK

This command saves all files on the shadow set $7$DUS2 that have been
created or modified since the last backup and records the current time as their
new backup date.

2-19

The Command-Level Interface
2. 7 Performing Backup Operations on a Shadow Set

2.7.3

Using BACKUP/IMAGE on a Shadow Set
You must take special precautions when you restore a shadow set from
a BACKUP /IMAGE save set. (See the VMS Backup Utility Manual for
a description of BACKUP /IMAGE operations with physical volumes.) A
BACKUP /IMAGE operation marks the target volume as more current than
the other shadow set members. This designates it as the source of copy
operations if you re-create the shadow set with it.
Although you can create BACKUP save sets or copies from shadow set
virtual units (not from active shadow set members), you should not mount
your shadow set with the /FOREIGN qualifier to allow a BACKUP /IMAGE
restoration. If you mount your Files-11 shadow set as a foreign shadow
set, you lose the automatic copy operations and error recovery normally
provided. DIGITAL does not support a restore operation from a BACKUP
/IMAGE save set to a virtual unit. You should either restore to a physical
disk and then re-create the shadow set with the restored disk as a shadow SE
member (example 2), or if the save was a copy to a compatible disk, re-creat
the shadow set with that disk as a member (example 3). The target of the
BACKUP /IMAGE operation becomes the source of copy operations if you
re-create the shadow set with it.
Example 1

This example shows how to perform a backup on a former shadow set
member after you rebuild the shadow set.
$ MOUNT $1$DUSO:/SHADOW = ($1$DUA10:, $1$DUA11:) GHOSTVOL
%MOUNT-I-MOUNTED, GHOSTVOL
mounted on _$1$DUSO: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA10: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMSUCC, _$1$DUA11: (HSC001) is now a valid member of
the shadow set

This command mounts the shadow set $1$DUSO. Make sure all copy
operations are finished before you dismount the shadow set with the
following command:
$ DISMOUNT $1$DUSO:

This command dismounts the shadow set. Do not list an active shadow set
member as the input specifier of a backup operation. You must dismount th
shadow set first.
$ MOUNT/SYSTEM DUSO/SHADOW=$1$DUA10: GHOSTVOL
%MOUNT-I-MOUNTED, GHOSTVOL
mounted on _$1$DUSO: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA10: (HSC001) is now a valid member of
the shadow set

This command puts the shadow set back on line without $1$DUA11. You
can now perform the backup to tape while the shadow set is on line.
$ MOUNT $1$DUA11: GHOSTVOL
%MOUNT-W-VOLSHDWMEM, mounting a shadow set member volume;
volume write locked
%MOUNT-I-MOUNTED, GHOSTVOL mounted on _$1$DUA11: (HSC001)
$ MOUNT/FOREIGN MTAO:
%MOUNT-I-MOUNTED,

2-20

The Command-Level Interface
2. 7 Performing Backup Operations on a Shadow Set

These two commands mount the former shadow set member and a magnetic
tape in preparation for a BACKUP command.
$ BACKUP/IMAGE $1$DUA11: MTAO:SAVESET.BCK

This command produces a BACKUP/IMAGE save set from $1$DUA11 while
the shadow set is on line with $1$DUA10.

Example 2
This example shows how to restore a shadow set from an image save set.
DIGITAL does not support restoring an image save set directly to a shadow
set because the BACKUP output medium (the shadow set) must be mounted
as a foreign volume.
$ MOUNT/FOREIGN MTAO:
%MOUNT-I-MOUNTED,
$ MOUNT/FOREIGN/OVERRIDE=SHADOW_MEMBERSHIP $1$DUA10:
%MOUNT-I-MOUNTED,

These two commands mount the save set magnetic tape for input and the
former shadow set member for output of the restore operation.
$ BACKUP/IMAGE MTAO:SAVESET.BCK $1$DUA10:

This command restores $1$DUA10 from the save set.
$ DISMOUNT $1$DUA10:

This command dismounts the restored volume ready to be mounted in a
shadow set.
$ MOUNT/SYSTEM DUSO/SHADOW=($1$DUA10:, $1$DUA11:) GHOSTVOL
%MOUNT-I-MOUNTED, GHOSTVOL
mounted on _$1$DUSO: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA10: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMCOPY, _$1$DUA11: (HSC001) added to the shadow set
with a copy operation

This command mounts the shadow set with the restored shadow set member.
The output of the image backup operation has a newer generation than other
previous members of the shadow set. Therefore, $1$DUA10 (the restored
volume) is the source of a copy operation when you form the shadow set.

Example 3
This example illustrates a BACKUP /IMAGE copy operation on a shadow
set. The image backup operation compacts the files and free space. Because
you must mount the output device of such operations with the /FOREIGN
qualifier, you must take the following special steps:
$ MOUNT $1$DUSO:/SHADOW = ($1$DUA10:, $1$DUA11:) MEANDMY
%MOUNT-I-MOUNTED, MEANDMY
mounted on _$1$DUSO: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA10: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMSUCC, _$1$DUA11: (HSC001) is now a valid member of
the shadow set
$ MOUNT/FOREIGN $1$DUA20:
%MOUNT-I-MOUNTED,

2-21

The Command-Level Interface
2. 7 Performing Backup Operations on a Shadow Set

The first command mounts the shadow set $1$DUSO. The second command
mounts, on $1$DUA20, the volume to be the output of the BACKUP /IMAGI
operation. The /FOREIGN qualifier is required.
$BACKUP/IMAGE

$1$DUSO: $1$DUA20:

This command performs the image backup using the virtual unit name as
the input specifier. The image backup operation compacts the files and free
space. Thus, the image backup copy of a shadow set has a newer generation
than the existing members in the shadow set.
$DISMOUNT $1$DUA20:
$ DISMOUNT $1$DUSO:

These commands dismount the target of the image backup and the shadow
set, in preparation for re-creating the shadow set. Note that when you recreate the shadow set, you lose any data written to the shadow set between
the start of the backup operation and dismounting.
$MOUNT/SYSTEM DUSO/SHADOW=($1$DUA10:, $1$DUA11:, $1$DUA20:) MEANDMY
%MOUNT-I-MOUNTED, MEANDMY
mounted on _$1$DUSO: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA20: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMCOPY, _$1$DUA10: (HSC001) added to the shadow set
with a copy operation
%MOUNT-I-SHDWMEMCOPY, _$1$DUA11: (HSC001) added to the shadow set
with a copy operation

This command rebuilds the shadow set with the image backup disk as one oJ
the shadow set members. The other former shadow set members receive full
copy operations.

2.8

Maintaining a Shadow Set
Generally, the user and the system access a shadow set through the virtual
unit. Occasionally, you may want to change an individual shadow set
member and then pass the changed data to the other shadow set members.
For example, you can run the VMS Data Compression/Expansion (DCX)
routines on a disk and then change the data on other shadow set members a~
well.
The following series of commands demonstrates how you can dissolve and
re-create the shadow set to perform specialized processes on one shadow set
member and transfer the change to the other shadow set members.
$MOUNT $45$DUS9: /SHADOW=($45$DUA2:, $45$DUA4:, $45$DUA8:) LURK1

This command mounts a shadow set with three shadow set members.
$ DISMOUNT/NOUNLOAD $45$DUS9:

This command dissolves the shadow set mounted in the previous command,
and makes the individual shadow set members available.
$MOUNT /OVERRIDE=SHADOW_MEMBERSHIP $45$DUA2:

2-22

LURK1

The Command-Level Interface
2.8 Maintaining a Shadow Set

This command mounts one former shadow set member as a Files-11
volume outside of the shadow set. To have write access, you must use
the /OVERRIDE=SHADOW_MEMBERSHIP qualifier. At this point, you can
process the volume as you would any physical disk. For example, you can
run the DCX routines on $45$DUA2. See the VMS Utility Routines Manual
for information about these routines.
$MOUNT

$45$DUS9: /SHADOW=$45$DUA2:

LURK1

This command re-creates the shadow set with only the processed volume as a
shadow set member.
Note that mounting $45$DUA2 with the /OVERRIDE=SHADOW_
MEMBERSHIP qualifier automatically erases the volume shadowing
generation number. If you mount all the former members of the shadow
set at the same time, MOUNT copies to the processed volume, considering it
an unrelated volume. The processing of $45$DUA2 would be lost.
You then add the other two former shadow set members to the new shadow
set producing automatic full copy operations on each.
$MOUNT

$45$DUS9:

/SHADOW=($45$DUA4:, $45$DUA8:)

LURK1

In this command $45$DUA4 and $45$DUA8 are added to the shadow set
$45$DUS9. This re-creates the original shadow set, except that each shadow
set member now has the benefits of processing that you cannot perform on
an intact shadow set.

2-23

Performing Shadow Set Operations with System
Services
Volume shadowing uses enhancements to three VMS system services to
perform shadow set operations.
•

$MOUNT-Creates, mounts, and adds members to shadow sets.

•

$DISMOU-Dismounts, dissolves, and removes members from shadow
sets.

•

$GETDVI-Returns information about shadow set virtual units and
members.

This chapter explains how to use these services to perform shadow set
operations. It does not contain a detailed description of each service. For
more information about the $MOUNT, $DISMOU, and $GETDVI services,
see the VMS System Services Reference Manual.

3.1

Using $MOUNT to Create and Mount Shadow Sets
You can use the $MOUNT system service to create shadow sets, to mount
shadow sets, and to add members to existing shadow sets. Calls to $MOUNT
that create, mount, or add members to shadow sets share the same syntax. To
direct the system to perform any of these mount operations, you construct a
$MOUNT item list. The item list specifies the virtual unit that represents the
shadow set and the members (physical devices) that the shadow set contains.
For example, to create and mount a new shadow set, your program calls
$MOUNT and specifies an item list that contains the names of the virtual unit
and the members. Later, if you want to add a member to the shadow set, you
make another call to $MOUNT that specifies an item list that contains the
name of the virtual unit and the name of the member you want to add to the
shadow set.
The call to $MOUNT has the following format:
SYS$MOUNT itmlst

The sections that follow describe each of the four $MOUNT shadow set item
codes in detail. They also explain how to construct a valid $MOUNT item list
and give examples of three $MOUNT shadow set item lists.
For a complete description of the $MOUNT service and its argument, see the

VMS System Services Reference Manual.

3-1

Performing Shadow Set Operations with System Services
3.1 Using $MOUNT to Create and Mount Shadow Sets

3.1.1

$MOUNT Shadow Set Item Codes
The list that follows explains the four $MOUNT shadow set item codes.
The item code MNT$_SHANAM specifies the virtual unit. The other three,
MNT$_SHAMEM, MNT$_SHAMEM_COPY, and MNT$_SHAMEM_
MGCOPY, specify members. In addition, the MNT$_FLAGS item code
contains two options that pertain to shadow set operations.
When you mount a Files-11 shadow set, the system determines the type
of copy operation a member requires before it can join the shadow set.
Therefore, you can use the MNT$_SHAMEM item code to specify any
member, regardless of the copy operation the member requires.
When you mount a foreign shadow set (a shadow set mounted as a foreign
volume), you must indicate the copy operation a member requires before
it can join the shadow set. You indicate the required copy operation by
specifying the member with one of the following item codes: MNT$_
SHAMEM, MNT$_SHAMEM_COPY, or MNT$_SHAMEM_MGCOPY.
The item code descriptions explain when to use the different item codes to
add members to a foreign shadow set.

MNT$_SHANAM
The MNT$_SHANAM item code specifies the name of the virtual unit to be
mounted. The buffer must contain a character string from 1 to 64 characters,
which is the virtual unit name. The virtual unit name may be a logical name;
if it is a logical name, it must translate to a virtual unit name. The name
should include the controller letter S, which indicates that the device is a
virtual unit.
Because every shadow set is represented by a virtual unit, you must include
at least one MNT$_SHANAM item descriptor in the item list that you pass
to $MOUNT to create and mount the shadow set. If you are mounting a
Files-11 volume set containing more than one shadow set, you must include
one MNT$_SHANAM item descriptor for each virtual unit included in the
volume set.
The relative position of the item descriptors in the item list determines the
membership of the shadow set. That is, it indicates which members should
be bound to a specific virtual unit to form the shadow set. You must first
specify the virtual unit by using the MNT$_SHANAM item code. Then,
you can specify any number of members that are to be represented by that
virtual unit by using one of the following item codes: MNT$_SHAMEM,
MNT$_SHAMEM_MGCOPY, or MNT$_SHAMEM_COPY. If you specify
one shadow set and want to specify a second, specify a second virtual unit
item descriptor. The members you specify subsequently are bound to the
shadow set represented by the virtual unit specified in the second virtual unit
item descriptor.

MNT$_SHAMEM
The MNT$_SHAMEM item code specifies the name of a member (physical
device) to be added to the shadow set represented by the most recently
specified virtual unit, that is, the virtual unit name specified in the most
recent MNT$_SHANAM item descriptor. The buffer must contain a character
string from 1 to 64 characters, which is the device name. The device name
may be a physical device name or a logical name; if it is a logical name, it
must translate to a physical device name.

3-2

Performing Shadow Set Operations with System Services
3.1 Using $MOUNT to Create and Mount Shadow Sets

If you are mounting a foreign shadow set, the MNT$_SHAMEM item code
indicates that the member specified in the item descriptor does not require a
shadow copy before it joins the shadow set.

When you mount a foreign shadow set, the system considers the first member
you specify after the virtual unit item descriptor to be the most current
member of the shadow set. The system makes copies to other members based
on this member. You must use the MNT$_SHAMEM item code to specify
the first member of a foreign shadow set, because it can never require a copy
operation before joining the shadow set.
To be valid, an item list must contain at least one item descriptor specifying
a member; this item descriptor must appear after the MNT$_SHANAM item
descriptor.

MNT$_SHAMEM_COPY
The MNT$_SHAMEM_COPY item code specifies the name of a member
to be added to the shadow set represented by the most recently specified
virtual unit, that is, the virtual unit name specified in the most recent MNT$_
SHANAM item descriptor. The buffer must contain a character string from
1 to 64 characters, which is the device name. The device name may be
a physical device name or a logical name; if it is a logical name, it must
translate to a physical device name.
When mounting a foreign shadow set, use the MNT$_SHAMEM_COPY item
code to indicate that the member specified in the item descriptor requires a
full copy operation before it can join the shadow set:

MNT$_SHAMEM_MGCOPY
The MNT$_SHAMEM_MGCOPY item code specifies the name of a member
to be added to the shadow set represented by the most recently specified
virtual unit, that is, the virtual unit specified in the most recent MNT$_
SHANAM item descriptor. The buffer must contain a character string from
1 to 64 characters, which is the device name. The device name may be
a physical device name or a logical name; if it is a logical name, it must
translate to a physical device name.
When mounting a foreign shadow set, use the MNT$_SHAMEM_MGCOPY
item code to indicate that the member specified in the item descriptor requires
a merge copy operation before it can join the shadow set.

MNT$_FLAGS
The MNT$JLAGS item code specifies a longword bit vector wherein each
bit specifies an option for the mount operation. The buffer must contain a
longword, which is the bit vector.
The $MNTDEF macro defines symbolic names for each option (bit) in the bit
vector. You construct the bit vector by specifying the symbolic names for the
desired options in a logical OR operation. The following table describes the
symbolic names for each shadow set option.

3-3

Performing Shadow Set Operations with System Service~
3.1 Using $MOUNT to Create and Mount Shadow Sets

Option

Description

MNT$V_NOCOPY

Disables full copy operations on all physical devices
being mounted or added to a shadow set. This
option provides you with the opportunity to confirm
the states of all of the members of a shadow set
before proceeding with any full copy operation. This
prevents any accidental loss of data that could occur
if an unintended device is added to the shadow set.
If you do not select this option, $MOUNT
automatically overwrites the data on shadow set
members that are not current. When you select
this option, a $MOUNT operation fails if any of the
specified potential shadow set members require full
copy operations.

MNT$V_OVR_SHAMEM

Allows you to mount former shadow set members
outside of the shadow set. If you do not specify this
option, $MOUNT automatically mounts the volume
write-locked to prevent accidental deletion of data.
To specify this option, you must either own the
volume or have VOLPRO privilege.
When you use this option, the shadow set generatior
number is erased from the volume. If you then
remount the volume in the former shadow set,
$MOUNT considers it an unrelated volume and marks
it for a full copy operation.

3.1.2

Constructing the $MOUNT Item List
When you construct a $MOUNT item list to create, mount, or add a member
to a shadow set, there are five important things to remember.

Every item list that mounts a shadow set must contain at. least one item
descriptor that specifies the virtual unit, and at least one item descriptor
that specifies a member (most shadow sets have at least two members).

The item descriptor that specifies the virtual unit must come before the
item descriptors that specify the members contained in the shadow set.

When mounting a Files-11 volume set, your item list must contain an
item descriptor for each virtual unit. The virtual unit item descriptor mm
be followed by item descriptors specifying the members to be representec
by that virtual unit.

If you are mounting a foreign shadow set, the item descriptor that

specifies the most current member of the shadow set must come after
the virtual unit item descriptor, and before any other member item
descriptors. The item descriptor must specify the MNT$_SHAMEM item
code to indicate that the member does not require a copy operation befor
joining the shadow set.

3-4

When you are specifying the members of a foreign shadow set, you mus
use the item code that specifies the type of copy operation that each
member must receive before it can join the shadow set. Following are th
item codes and the copy operations they specify.

Performing Shadow Set Operations with System Services
3.1 Using $MOUNT to Create and Mount Shadow Sets

3.1.3

Item Code

Copy Operation

MNT$_SHAMEM

The member does not require a copy
operation before it joins the shadow
set.

MNT$_SHAMEM_COPY

The member requires a full copy
operation before it joins the shadow
set.

MNT$_SHAMEM_MGCOPY

The member requires a merge copy
operation before it joins the shadow
set.

Examples of $MOUNT Item Lists
The examples in this section show $MOUNT item lists for some typical
shadow sets. The first example shows the type of item list you would
construct to create and mount a Files-11 shadow set. The second example
shows the type of item list you would construct to create and mount a
Files-11 volume set that contains two shadow sets. The final example shows
the type of item list you would construct to create and mount a foreign
shadow set.
Item List for Files-11 Shadow Set
This example shows the MACR0-32 statements required to produce a
$MOUNT system service item list to mount a Files-11 shadow set. A call
to $MOUNT specifying the item list that follows performs the same action as
the following DCL command MOUNT.
$ MOUNT $4$DUS23: /SHADOW = ( $4$DUA9:, $4$DUA5:, $4$DUA10: ) _$ MYVOLUME DISK$MYVOLUME
S_$4$DUS23: .ASCII /$4$DUS23:/
S_$4$DUA9:
.ASCII /$4$DUA9:/
S_$4$DUA5:
.ASCII /$4$DUA5:/
S_$4$DUA10: .ASCII /$4$DUA10:/
S_LABEL: .ASCII /MYVOLUME/
S_LOGNM: .ASCII /DISK$MYVOLUME/
.MACRO
.ITEM, SIZE, CODE, BUFFER, RETURN=O
.WORD
SIZE, CODE
.ADDRESS BUFFER, RETURN
.ENDM
. ITEM
ITMLST: . ITEM
. ITEM
. ITEM
.ITEM
. ITEM
.ITEM
.LONG

MNT$_SHANAM, S_$4$DUS23
MNT$_SHAMEM, S_$4$DUA9
MNT$_SHAMEM, S_$4$DUA5
MNT$_SHAMEM, S_$4$DUA10
MNT$_VOLNAM, S_LABEL
13, MNT$_LOGNAM, S_LOGNM
0, 0, 0

8,
8,
9,
8,

0
8

e
e

Notice that the virtual unit item descriptor occurs first. This item
descriptor specifies $4$DUS23 as the name of the virtual unit. The
controller letter S indicates that the device is a virtual unit.

3-5

Performing Shadow Set Operations with System Services
3.1 Using $MOUNT to Create and Mount Shadow Sets

The virtual unit item descriptor is followed by three member item
descriptors. Because the system determines the type of copy operation
necessary before Files-11 disks can join a Files-11 shadow set, all of the
members are mounted with MNT$_SHAMEM item descriptors. These
item descriptors specify that $4$DUA9, $4$DUA5, and $4$DUA10 are to
join the shadow set represented by $4$DUS23.

The member item descriptors are followed by an item descriptor that
specifies the volume label for the shadow set as MYVOLUME.

The last item descriptor specifies the logical name for the shadow set as
DISK$MYVOLUME.

Item List for Files-11 Volume Set

This example shows the MACR0-32 statements required to produce a
$MOUNT system service item to mount a Files-11 volume set that contains
two shadow sets. A call to $MOUNT specifying the item list that follows
performs the same action as the following DCL command MOUNT.
$ MOUNT
$4$DUS23: /SHADOW= ( $4$DUA9:, $4$DUA5:, $4$DUA10: ),_$
$4$DUS51: /SHADOW= ( $4$DUA12:, $4$DUA3:, $4$DUA34: ) _$
WORK1,WORK2 WRKD$
S_$4$DUS23: .ASCII /$4$DUS23:/
S_$4$DUS51: .ASCII /$4$DUS51:/
S_$4$DUA9:
.ASCII /$4$DUA9:/
S_$4$DUA5:
.ASCII /$4$DUA5:/
S_$4$DUA10: .ASCII /$4$DUA10:/
S_$4$DUA12: .ASCII /$4$DUA12:/
S_$4$DUA3:
.ASCII /$4$DUA3:/
S_$4$DUA34: .ASCII /$4$DUA34:/
S_WORK1: .ASCII /WORK1/
S_WORK2: .ASCII /WORK2/
S_LOGNM: .ASCII /WRKD$/
.MACRO
.ITEM, SIZE, CODE, BUFFER, RETURN=O
.WORD
SIZE, CODE
.ADDRESS BUFFER, RETURN
.ENDM
. ITEM
ITMLST: .ITEM
.ITEM
. ITEM
. ITEM
. ITEM
. ITEM
.ITEM
.ITEM
.ITEM
.ITEM
.ITEM
.LONG

3-6

9, MNT$_SHANAM, S_$4$DUS23
8, MNT$_SHAMEM, S_$4$DUA9
8, MNT$_SHAMEM, S_$4$DUA5

0
8

9, MNT$_SHAMEM, S_$4$DUA10
5, MNT$_VOLNAM, S_WORK1
9, MNT$_SHANAM, S_$4$DUS51 0
9, MNT$_SHAMEM, S_$4$DUA12 0
8, MNT$_SHAMEM, S"'""$4$DUA3
9, MNT$_SHAMEM, S_$4$DUA34
5, MNT$_VOLNAM, S_WORK2
0
5, MNT$_LOGNAM, S_LOGNM
0
0, 0, 0

•

Notice that the virtual unit item descriptor for the first volume in the
volume set occurs first. This item descriptor specifies $4$DUS23 as the
name of the first virtual unit in the volume set.

The virtual unit item descriptor is followed by item descriptors for each
of the members that are to be represented by the first virtual unit:
$4$DUA9, $4$DUA5, and $4$DUA10.

Performing Shadow Set Operations with System Services
3.1 Using $MOUNT to Create and Mount Shadow Sets

The member item descriptors are followed by an item descriptor that
specifies the volume label for the first shadow set in the volume set as
WORKl.

Following the descriptors for the first shadow set in the volume set are
similar item descriptors for the second shadow set in the volume set.
These item descriptors specify the second virtual unit as $4$DUS51; the
members as $4$DUA12, $4$DUA3, and $4$DUA34; and the volume label
as WORK2.

The last item descriptor specifies the logical name for the entire volume
set as WRKD$.

Item List for Foreign Shadow Set

This example shows the MACR0-32 statements required to produce a
$MOUNT system service item list to mount a foreign shadow set. A call
to $MOUNT specifying the item list that follows performs the same action as
the following DCL command MOUNT.
$ MOUNT /FOREIGN $4$DJS8: _$ /SHADOW = (NO_COPY=$4$DJA4:, MERGE_COPY=$4$DJA18:, COPY=$4$DJA12:
FLAGS:
S_DJS8:
S_DJA4:
S_DJA18:
S_DJA12:

.LONG MNT$M_FOREIGN
.ASCII /$4$DJS8:/
.ASCII /$4$DJA4:/
.ASCII /$4$DJA18:/
.ASCII /$4$DJA12:/
.MACRO
.ITEM, SIZE, CODE, BUFFER, RETURN=O
.WORD
SIZE, CODE
.ADDRESS BUFFER, RETURN
.ENDM
. ITEM

ITMLST: .ITEM
. ITEM
.ITEM
.ITEM
. ITEM
.LONG

4, MNT$_FLAGS,
8, MNT$_SHANAM,
8, MNT$_SHAMEM,
9, MNT$_SHAMEM_MGCOPY,
9, MNT$_SHAMEM_COPY,

FLAGS
S_$4$DJS8 0
S_$4$DJA4 8
S_$4$DJA18 8
S_$4$DJA12 0

0, 0, 0

The second item descriptor specifies the virtual unit $4$DJS8.

The third item descriptor specifies the member that is considered the
most current member of the shadow set. Because this member, $4$DJA4,
doesn't need to have any information copied to it, it is specified with a
MNT$_SHAMEM item descriptor.

The fourth item descriptor specifies the member $4$DJA18. It is specified
with the MNT$_SHAMEM_MGCOPY item descriptor, because it needs
a merge copy operation before it can join the shadow set.

The last item descriptor specifies the member $4$DJA12. It is specified
with the MNT$_SHAMEM_COPY item descriptor, because it needs a
full copy operation before it can join the shadow set.

3-7

Performing Shadow Set Operations with System Services
3.1 Using $MOUNT to Create and Mount Shadow Sets

3.1.4

Evaluating Condition Values Returned by $DISMOU, $MOUNT, and
$QIO
This section contains information about the condition values returned by
$DISMOU, $MOUNT, and $QIO that pertain to mounting and using shadow
sets. For a complete list of the condition values returned by these services,
see the VMS System Services Refere nee Manual.
If $MOUNT returns the condition value SS$_BADP ARAM, your item list
probably contains one of the following errors:

•

The virtual unit specified in one of your MNT$_SHANAM item
descriptors contains a controller letter other than the letter S. The
controller letter S designates that a device is a shadow set virtual unit.

•

A MNT$_SHAMEM item descriptor appears in the item list before any
MNT$_SHANAM item descriptor.

•

Your item list contains a MNT$_SHANAM item descriptor, but it is
not followed by any of the following three item descriptors: MNT$_
SHAMEM, MNT$_SHAMEM_MGCOPY, or MNT$_SHAMEM_COPY.

•

A MNT$_DEVNAM item descriptor appears in the item list in the middle
of a series of item descriptors that specify a single shadow set. It is
possible to construct a Files-11 volume set that contains one or more
nonshadowed disks, as well as one or more shadow sets. However,
when you use the MNT$_DEVNAM item descriptor to specify the
nonshadowed disk, it must not appear in between the MNT$_SHANAM
item descriptor that specifies a virtual unit and the item descriptors that
specify the members of the shadow set that the virtual unit represents.

When you are mounting and using foreign shadow sets, your program must
handle changes in shadow set membership. After making a call to $QIO,
your program should check the $QIO 1/0 status block for the following
condition values, which signal a change in shadow set membership:
SS$_VOLINV
SS$_SHACHASTA
SS$_MEDOFL
If you make a call to $DISMOU to dismount a device on which a copy
operation is in progress, $DISMOU returns the condition value SS$_
DEVACTIVE.

3.2

Using $DISMOU to Dismount Shadow Sets
You can use $DISMOU to perform the following three shadow set operations
•

Remove a member from a shadow set.

•

Dismount a shadow set on a single node.

•

Dismount and dissolve a shadow set.

The call to $DISMOU has the following format:
SYS$DISMOU devnam ,flags

The action $DISMOU takes depends in part on whether you specify a shadov
set virtual unit or a shadow set member in the devnam argument.

3-8

Performing Shadow Set Operations with System Services
3.2 Using $DISMOU to Dismount Shadow Sets

For a complete description of the $DISMOU service and its arguments, see
the VMS System Services Reference Manual.

3.2.1

Removing Member Units from Shadow Sets
If you want to remove a single member from a shadow set, you must make
a call to $DISMOU. In the devnam argument, you should specify the name
of the shadow set member you want to remove. As a result of this call, all
nodes in the cluster that have the shadow set mounted remove the member
from the shadow set. This is the software-induced equivalent to a hardware
failure that causes the remote server to remove a member from a shadow set.

When you remove a member from a shadow set, and the system is in the
process of writing information to that member, the writing in progress at the
time of removal may not be completed. Therefore, information contained
in any files that are open when the member is removed is unreliable.
The specified member is spun down unless you specify the DMT$M_
NOUNLOAD option in the flags argument.
The following example demonstrates a call to $DISMOU that removes the
member $2$DUA9 from the shadow set represented by the virtual unit
$2$DUS34.
Removing a Member
$DMTDEF
FLAGS: .LONG 0
S_$2$DUA9:
.ASCID /$2$DUA9:/

$DISMOU_S devnam = S_$2$DUA9, flags = FLAGS

.END

3.2.2

Dismounting and Dissolving Shadow Sets
If you want to dismount a shadow set on a single node, you must make a
call to $DISMOU. In the devnam argument, you should specify the name of
the virtual unit that represents the shadow set you want to dismount. If you
only want to dismount the shadow set, you should not specify the DMT$M_
CLUSTER option in the flags argument of the call.

When you dismount a shadow set on a single node in a VAXcluster and
other nodes in the VAXcluster still have the shadow set mounted, none of
the shadow members contained in the shadow set are spun down even if you
have not specified the DMT$M_NOUNLOAD flag. After this call completes,
the shadow set is unavailable on the node from which the call was made.
The shadow set is still available to other nodes in the cluster that have the
shadow set mounted.

3-9

Performing Shadow Set Operations with System Service~
3.2 Using $DISMOU to Dismount Shadow Sets

If the node on which the shadow set is being dismounted is the only node
that has the shadow set mounted, the HSC dissolves the shadow set. The
shadow set members are spun down, unless you specify the DMT$M_
NOUNLOAD flag.

In the following example, $DISMOU dismounts the shadow set represented
by the virtual unit $4$DUS23.
Dismounting a Shadow Set
$DMTDEF
FLAGS:
.LONG 0
S_$4$DUS23: .ASCID /$4$DUS23:/

$DISMOU_S devnam = S_$4$DUS23, flags = FLAGS

.END

If you want to dissolve the shadow set, make a call to $DISMOU specifying
the name of the virtual unit that represents the shadow set you want to
dismount and dissolve. You must specify the DMT$M_CLUSTER option in
the flags argument so that the shadow set is dismounted from every node
in the cluster. When each node in the cluster has dismounted the shadow
set (the count of hosts having the shadow set mounted reaches 0), the HSC
dissolves the shadow set.

When a shadow set is dissolved, there is no longer any meaningful
relationship between either the virtual unit and the shadow set members,
or among the shadow set members. The member units can be mounted as
single disks for other purposes. The virtual unit changes to a medium offline
state. As a part of the dissolve operation, all shadow set members are spun
down, unless you specify the DMT$M_NOUNLOAD opfion in the call to
$DISMOU.
In the following example, $DISMOU dismounts the shadow set represented
by the virtual unit $4$DUS23. The call dismounts the shadow set clusterwidE:
Therefore, when the shadow set is dismounted from the last node, the HSC
dissolves the shadow set.
Dismounting and Dissolving a Shadow Set
$DMTDEF
FLAGS:
.LONG DMT$M_CLUSTER
S_$4$DUS23: .ASCID /$4$DUS23:/

$DISMOU_S devnam = S_$4$DUS23, flags = FLAGS

.END

3-10

Performing Shadow Set Operations with System Services
3.2 Using $DISMOU to Dismount Shadow Sets

3.2.3

Setting $DISMOU Flags in Shadow Set Operations
The following table lists the options for the $DISMOU flags argument
and describes the shadow set operations that use these options. For a full
description of each of these flag options, see the description of the $DISMOU
service in the VMS System Services Reference Manual.

3.3

Option

Description

DMT$M_UNLOAD

Legal for all shadowing-related requests

DMT$M _CLUSTER

Legal for all shadowing-related requests

DMT$M_ABORT

Honored for virtual units; ignored for member units

DMT$M_UNIT

Ignored for virtual units and their members

Using $GETDVI to Obtain Information About Shadow Sets
The $GETDVI system service is useful for obtaining information about the
shadow set devices on your system. Through the use of the shadow set item
codes, you can determine the following types of information:
•

Whether a device is a shadow set virtual unit or a shadow set member

•

Whether a copy operation is in progress on a device

•

What type of copy operation is in progress on a device

•

The name of the virtual unit that represents the shadow set of which the
particular device is a member

•

The entire membership of a shadow set, including the virtual unit and all
of the members

•

Whether a member has been removed from the shadow set by the remote
server

The call to $GETDVI has the following format:
SYS$GETDVI [efn] ,[chan] ,[devnam] ,itmlst ,[iosb]
,[astadr] ,[astprm] ,[nullarg]

For a complete description of the $GETDVI and $GETDVIW services and
their arguments, see the VMS System Services Reference Manual.

3.3.1

$GETDVI Shadow Set Item Codes
This section contains a list that explains the information returned by the
$GETDVI shadow set item codes.

DVl$_SHDW_CATCHUP_CQPYING
When you specify DVJ$_SHDW_CATCHUP_COPYING, $GETDVI returns
a longword, which is interpreted as Boolean. The value 1 indicates that the
device is a member receiving a full copy operation before joining a shadow
set.

3-11

Performing Shadow Set Operations with System Services
3.3 Using $GETDVI to Obtain Information About Shadow Sets

DVl$_SHDW_fAILED_MEMBER
When you specify DVI$_SHDW_FAILED_MEMBER, $GETDVI returns a
longword, which is interpreted as Boolean. The value 1 indicates that the
device is a member that has been removed from the shadow set by the
remote server.
DVl$_SHDW_MASTER
When you specify DVI$_SHDW_MASTER, $GETDVI returns a longword,
which is interpreted as Boolean. The value 1 indicates that the device is a
virtual unit.
DVl$_SHDW_MASTER_NAME
When you specify DVI$_SHDW_MASTER_NAME and the specified device
is a shadow set member, $GETDVI returns the device name of the virtual unit
that represents the shadow set of which the specified device is a member.
$GETDVI returns a null string if the specified device is not a member, or is,
itself, a virtual unit.
When the shadow set members are dual pathed to two HSCs and, therefore,
have a nonzero allocation class, the device name returned by $GETDVI
contains the allocation class; the name has the form $allocation-class$device.
For example, if a virtual unit has an allocation class of 255 and the device
name DUSlO, $GETDVI returns the following string: $255$DUS10.
When the shadow set members have a zero allocation class, the device
name contains the HSC node name; the name has the form hsc$device. For
example, if the node name of the HSC is LAMONT and the device name is
DUSlO, $GETDVI returns the following string: LAMONT$DUS10.
Because the shadow set virtual unit name can include up to 64 characters, the
buffer length field of the item descriptor should specify 64 (bytes).

DVl$_SHDW_MEMBER
When you specify DVI$_SHDW_MEMBER, $GETDVI returns a longword,
which is interpreted as Boolean. The value 1 indicates that the device is a
shadow set member.
DVl$_SHDW_MERGE_CQPYING
When you specify DVI$_SHDW_MERGE_COPYING, $GETDVI returns a
longword, which is interpreted as Boolean. The value 1 indicates that the
device is a member receiving a merge copy operation before joining a shadow
set.
DVl$_SHDW_NEXT_MBR_NAME
When you specify DVI$_SHDW_NEXT_MBR_NAME, $GETDVI returns the
device name of the next member in the shadow set. If you specify a virtual
unit, $GETDVI returns the device name of the lowest-numbered member.
If you specify a member, $GETDVI returns the device name of the member
with the next highest number. If you specify the device name of the highestnumbered member, $GETDVI returns a null string. If you specify the name
of a device that is neither a virtual unit nor a member, $GETDVI returns a
null string.
$GETDVI returns the device name of the next member in the shadow set
even if the remote server has removed the next member from the shadow set.

3-12

Performing Shadow Set Operations with System Services
3.3 Using $GETDVI to Obtain Information About Shadow Sets

When the shadow set members are dual pathed to two HSCs and therefore
have a nonzero allocation class, the device name returned by $GETDVI
contains the allocation class; the name has the form $allocation-class$device.
For example, if a shadow set has an allocation class of 255 and the device
name is DUSlO, $GETDVI returns the following string: $255$DUS10.
When the shadow set members have a zero allocation class, the device
name contains the HSC node name; the name has the form hsc$device. For
example, if the node name of the HSC is LAMONT and the device name is
DUSlO, $GETDVI returns the following string: LAMONT$DUS10.
Because a device name can include up to 64 characters, the buffer length field
of the item descriptor should specify 64 (bytes).

3.3.2

Obtaining the Names of All Members of a Shadow Set
To obtain the names of all members of a shadow set, you must make a series
of calls to $GETDVI. In your first call to $GETDVI you can specify either
the device name of the virtual unit that represents the shadow set whose
membership you want to determine, or the device name of a member of the
shadow set.
Starting with the Shadow Set Virtual Unit
If your first call specifies the name of the virtual unit, the item list should
contain a DVl$_SHDW_NEXT_MBR_NAME item descriptor into which
$GETDVI returns the name of the lowest-numbered member of the shadow
set. The devnam argument of the next call to $GETDVI should specify the
device name returned in the previous call's DVl$_SHDW_NEXT_MBR_
NAME item descriptor. This second call's item list should contain a DVI$_
SHDW_NEXT_MBR_NAME item descriptor to receive the name of the next
highest-numbered unit in the shadow set. You should repeat these calls to
$GETDVI until $GETDVI returns a null string, which means that there are no
more members in the shadow set.

Starting with a Shadow Set Member Unit
If your first call specifies the name of a shadow set member, you must
determine the name of the virtual unit that represents the shadow set before
you can obtain the names of all members contained in the shadow set.
Therefore, if your first call specifies a member, it should also specify an
item list that contains a DVI$_SHDW_MASTER_NAME item descriptor.
$GETDVI returns the name of the virtual unit that represents the shadow
set into this descriptor. Now, you are ready to make the series of calls to
$GETDVI described previously. The devnam argument of each call specifies
the name of the device returned in the previous call' s DVl$_SHDW_NEXT_
MBR_NAME item descriptor. You repeat these calls until $GETDVI returns a
null string, indicating that there are no more members in the shadow set.

The DVl$_SHDW_NEXT_MBR_NAME item code returns the names of
all members of the shadow set, even if the remote server has removed the
members from the shadow set. If you want to determine the names of all
the current members of the shadow set, you should use the DVl$_SHDW_
FAILED_MEMBER item code to identify and ignore members that have been
removed from the shadow set.

3-13

Licensing, Enabling, and Managing VAX Volume
Shadowing
This chapter briefly explains license registration, which authorizes the use of
VAX Volume Shadowing. It also describes system management issues related
to volume shadowing in a VAXcluster and on a system disk.

4.1

Registering the Volume Shadowing Product Authorization Key (PAK)
After you install and license VMS Version 5.0 by registering a VMS Product
Authorization Key (PAK), you must license VAX Volume Shadowing with a
separate Volume Shadowing PAK. Obtain a PAK, generally a paper certificate
similar to the one shown in Example 4-1, from a DIGITAL representative.
The PAK provides information that defines the VAX Volume Shadowing
license contract you have with DIGITAL. When you enter this information
into the online LICENSE database, the VMS License Management Facility
(LMF) authorizes use of volume shadowing. In some cases, a PAK may be
registered automatically when you install VMS or an update to VMS. See the
installation kit cover letter and the VMS release notes for the correct license
registration method.

Example 4-1

Example of a Product Authorization Key (PAK}

I I I I I I I I

ldlilgliltlalll

Product Authorization Key (PAK)

I I I I I I I I

Digital Equipment Corporation
Maynard, MA.
LICENSE ADMINISTRATION LOCATION:
Digital Equipment Corporation
Maynard, Ma.
Address

ORDERED BY: Casper Friendly
Data Twice, Inc.
Shady Hill, CT. 20010

********************************************************************************
PAK ID:

Issuer: DEC
Authorization Number: USA00326
PRODUCT ID:
Product Name: VOLSHAD
Producer: DEC
NUMBER OF UN ITS :
Number of Units: 1234

Example 4-1 Cont'd. on next page

4-1

Licensing, Enabling, and Managing VAX Volume Shadowing
4.1 Registering the Volume Shadowing Product Authorization Key (PAK)

Example 4-1 (Cont.)

Example of a Product Authorization Key (PAK}

KEY LEVEL:
Version: 5.0
Product Release Date:
KEY TERMINATION DATE:
Key Termination Date:
RATING:
Availability Table Code: E
Activity Table Code:
MISCELLANEOUS:
Key Options: MOD_UNITS
Product Token:
Hardware-Id:
Checksum: 1-MJLI-JEKC-GHBB-JGKB

********************************************************************************
After a Product Authorization Key is registered but before you can use
VAX Volume Shadowing, you must also set the System Generation Utility
(SYSGEN) SHADOWING parameter as descibed in Section 4.2.

4.2

Setting the SYSGEN Parameter for Volume Shadowing
After registering the volume shadowing Product Authorization Key (PAK),
you must invoke the System Generation Utility (SYSGEN) to set the
SHADOWING SYSGEN parameter. Invoke SYSGEN by typing the following:
$RUN SYS$SYSTEM:SYSGEN
SYSGEN>

Then, set the system parameter SHADOWING to 1 (volume shadowing), as
follows:
SYSGEN> SET SHADOWING 1
SYSGEN> WRITE CURRENT

Type EXIT or press CTRL/Z to return to the DCL level.
Finally, you must reboot the system.

Note: To ensure volume shadowing is enabled each time Autogen executes, edit
the file SYS$SYSTEM:MODPARAMS.DAT to use the DCL assignment
statement SHADOWING=l. See the Guide to Setting Up a VMS System for
more information about editing the MODPARAMS.DA T file.

4.3

Using Volume Shadowing on the System Disk
To use volume shadowing on the system disk, you must copy the new
primary bootstrap program, VMB, to your console device CSAl. If you are
using a VAXcluster, you must copy VMB to the console device of each node in
the cluster. Use the following commands:
$ RUN SYS$SYSTEM:SYSGEN
SYSGEN> CONNECT CONSOLE
SYSGEN> ICTRL/Z I
$ EXCHANGE COPY /LOG SYS$SYSTEM:VMB.EXE CSA1:

4-2

Licensing, Enabling, and Managing VAX Volume Shadowing
4.3 Using Volume Shadowing on the System Disk

After copying VMB to the console device, you must also modify
DEFBOO.CMD 1 as described in Section 4.4.

4.4

Booting from a System Disk Shadow Set
You can mount your system disk as a shadowed set, but you must take
special steps when creating the shadow set. If no system disk shadow set
currently exists, as it might if you have VAXcluster nodes booting from a
common disk, then the system must boot from one of the physical disks that
would typically be in a shadow set.
Normally, when you boot from an HSC disk, you deposit the unit number
of your system disk into boot register R3 (see the processor installation or
operations manual for details). For a system disk shadow set, however, you
must deposit in R3 both the virtual unit number and the unit number of one
of the shadow set members. You must convert the unit numbers of both
the virtual unit and the physical unit that is normally a shadow set member
into hexadecimal. You then deposit the unit number (in hexadecimal) of the
virtual unit number into the high word (bits <30:16> ) of boot R3, and
deposit the physical unit number (in hexadecimal) into the low word (bits
<15:0>) of R3. You must also set the sign bit (bit 31) to indicate that you
are using a shadow set virtual unit. Thus, if the system disk shadow set uses
a virtual unit number of OOOC (12 decimal) and a physical unit number of
0000, the deposit command line for a VAX 8600 should be like this:
>>> DEPOSIT R3 800COOOO

The same procedure on a VAX 8200 should look like this:
BOOT58> D/G

3 800COOOO

Note: You must deposit the same physical unit number into R3 of every
VAXcluster member. If VAXcluster members specify different shadow
set members for booting, you risk the loss of system crash information.
Also, you must deposit the physical unit number of the last existing
shadow set member. Do not identify as the boot member a physical unit
that is less current than another shadow set member. The system creates
a new shadow set by copying data from the identified boot member
without regard to which former member is most current. You can lose
data during the automatic copy operation.
Figure 4-1 presents a system configuration of a VAX 8600 and a VAX 8200 in
a VAXcluster with a system disk shadow set dual ported to a pair of HSCs.
The VAX CPUs have corresponding default boot command files. They specify
the location of the system disk shadow set and a physical device that is
normally one of the shadow set members.
This figure also illustrates matching site-specific system startup command files,
named SYSTARTUP_VS.COM. To have the system create a complete shadow
set at bootstrap time, a system manager must add a MOUNT command to
each SYSTARTUP_VS.COM that completely describes the desired system disk
shadow set.

This command file has different names, depending on the type of processor you are using. See Table 4-1 for
more information.

4-3

~c
~

(")

(I)

CD ::l
0

=· ::l-·
0

:::J

Figure 4-1

Booting from a System Disk Shadow Set

Example DEFBOO.COM file for VAX 8600

..,
m
0
::l
3 m
-t\

Example DEFBOO.CMD file for VAX 8200

en ::l

C"'

<CA (Q
r+

CD
Matching Unit Numbers

Example SYSTARTUP_V5.COM file

Matching MOUNT Commands

en cu
::J"'

::l

Q)
(Q

VAX 8600

::l

-· c.
~s

-·

~ ::l

en
<e
CD

VAX 8200

):>

><
<
2.
c

(I)
Cl PORT 14

Cl PORT 0

:::r
Q)

c.
0

::l

Licensing, Enabling, and Managing VAX Volume Shadowing
4.4 Booting from a System Disk Shadow Set

Note that different processors use different names for the default boot
command procedure. Table 4-1 provides the names of the files by processor
type.
Table 4-1

Names of Default Boot Command Procedures

Processor Names

Boot Command File Name

VAX 8800, VAX 8700, VAX 8550,
VAX 8530

DEFBOO.COM 1

v AX 8840 v AX 8830 v AX 8820
v AX 8650 v AX 8600

DEFBOO.CMD 1

VAX 8350, VAX 8300, VAX 8250,
VAX 8200

DEFBOO.CMD

VAX-11/785, VAX-11/780

DEFBOO.CMD

DEFBOO.COM

VAX-11/750

DEFBOO.CMD

VAX-11/730, VAX-11/725

DEFBOO.CMD

1 For volume shadowing, you must also edit BCIBOO.COM, BCIGEN.COM, BCIXDT.COM,
BDABOO.COM, BDAGEN.COM, BDAXDT.COM, UDABOO.COM, UDAGEN.COM, and
UDAXDT.COM. See the documentation for your specific processor.

4.5

Upgrading a System That Uses a System Disk Shadow Set
You cannot upgrade a shadowed system disk while it is in use as a shadow
set. The upgrade procedure must reboot at times when the necessary
shadowing support would not be available. Therefore, the upgrade procedure
terminates abnormally if a system disk shadow set is active.
When you are using a shadowed system disk, you must modify the procedure
to upgrade to a new version of VMS that is described in the VMS release
notes. First, you must create a nonshadowed system disk to be upgraded.
You can use standalone BACKUP to create a compressed copy of the shadow
set on a single scratch disk (a disk with no useful data), or you can remove
a current member from the system disk shadow set. Next, you perform the
upgrade on the copy of the system disk shadow set. Finally, you build a
new system disk shadow set using the updated disk as the source for shadow
copies to other members.
The Procedure

This procedure is divided into three parts. In Part 1, you convert the system
disk shadow set to a nonshadowed system disk.
Part 1
1

Select a VAXcluster member and a scratch disk (or current member of the
current shadowed system disk). with which to perform the upgrade.

Prepare a DEFBOO.CMD boot command file that boots from the selected
disk without shadowing (does not name a virtual unit in boot
register 3). Store this command procedure on the console media of the
system selected to perform the upgrade.

4-5

Licensing, Enabling, and Managing VAX Volume Shadowing
4.5 Upgrading a System That Uses a System Disk Shadow Set

On the VAXcluster member selected to perform the upgrade, invoke the
System Generation Utility (SYSGEN) by typing the following:
$ RUN SYS$SYSTEM:SYSGEN
SYS GEN>

If you are running a system previous to Version 5.0, disable volume
shadowing by setting system parameter VMS7 to 0, as follows:
SYSGEN> SET VMS7 0
SYSGEN> WRITE CURRENT

If you are running a system with Version 5.0 or later instead, disable
volume shadowing by setting system parameter SHADOWING to 0, as
follows:
SYSGEN> SET SHADOWING 0
SYSGEN> WRITE CURRENT

Type EXIT or press CTRL/ Z to return to the DCL level.

Shut down all systems that boot from the system disk shadow set,
including the one chosen to perform the upgrade. Dismount the shado'
set from any remaining VAXcluster members that have it mounted.

Note: At this point the shadow set should be dissolved; no VAXcluster
members should have it mounted.

If you have selected a scratch disk for the upgrade, read the restrictions
on standalone BACKUP described in Section 4.7. Then back up, with
standalone BACKUP, a former shadow set member from the old system
disk shadow set (that you just dissolved) to the selected scratch disk.
Your processor installation or operations manual describes how to use
standalone BACKUP on a system disk. If you are not using a scratch di
for the upgrade, go to Part 2 of the procedure.

In Part 2 you perform the upgrade.
Part 2
1

Using the upgraded DEFBOO.CMD file prepared in step 2, boot the
system chosen for the upgrade from the disk chosen to be upgraded.

Perform the upgrade on this single disk, as outlined in the VMS releasE
notes.

Register the VAX Volume Shadowing Product Authorization Key (PAKj
or keys, as described in the release notes and cover letter with your
installation kit.

Invoke the System Generation Utility (SYSGEN) by typing the followin
$ RUN SYS$SYSTEM:SYSGEN
SYSGEN>

To enable volume shadowing on a Version 5.0 system, set system
parameter SHADOWING to 1 (before Version 5.0, you set system
parameter VMS7), as follows:
SYSGEN> SET SHADOWING 1
SYSGEN> WRITE CURRENT

Note: To ensure volume shadowing is enabled each time Autogen
executes, edit the file SYS$SYSTEM:MODP ARAMS.DAT to use

4-6

Licensing, Enabling, and Managing VAX Volume Shadowing
4.5 Upgrading a System That Uses a System Disk Shadow Set

the DCL assignment statement SHADOWING=l. See the Guide to
Setting Up a VMS System for more information about editing the
MODPARAMS.DAT file.
Type EXIT or press CTRL/Z to return to the DCL level.

Restore the DEFBOO.CMD file to its original contents for shadow set
booting (see Section 4.4 for details).

Shut down the system performing the upgrade.

Exchange the unit plug of the physical unit normally named in boot
register R3 of the shadowing DEFBOO.CMD file with the unit plug of the
unit with the upgraded disk. This makes the VAXcluster members that
normally boot from the system disk shadow set use the newly upgraded
disk as the first member of a new system disk shadow set. At this point,
you may leave the disk formerly named as the first member off line to
preserve its contents.

In Part 3 you rebuild a system disk shadow set from the upgraded disk.
Part 3
1

Boot the VAXcluster members that boot from the system disk shadow set
and remount the shadow set on any remaining VAXcluster members.
Each VAXcluster node must use a DEFBOO.CMD file that selects the
upgraded system disk as the physical unit in boot R3. This ensures that
the upgraded disk becomes the source of a new system disk shadow set.
The site-specific startup command procedures name additional members
that are added to the new shadow set with full copy operations.

Copy the file SYS$SYSTEM:VMB.EXE from the upgraded system to all
console media of each VAXcluster member. See Section 4.3 for details.

If the VMS upgrade procedure directs you to use AUTOGEN,
you must do so on all the VAXcluster members. Edit the file
SYS$SYSTEM:MODPARAMS.DAT, as described in Part 2 of this
procedure.

Back up your new system disk shadow set. If you normally use
online BACKUP for this task, you can use a procedure described in
Section 2.7. If you normally use standalone BACKUP at this point,
read the restrictions described in Section 4.7. You must dismount the
system disk shadow set, and remove one member to use as the source of
standalone BACKUP. You can then remount the system disk shadow set
without the member designated for use with standalone BACKUP. Mount
that volume outside the shadow set.

4-7

Licensing, Enabling, and Managing VAX Volume Shadowing
4.6 Performance Information for Volume Shadowing

4.6

Performance Information for Volume Shadowing
This section offers some general recommendations and information related to
the performance characteristics of shadow sets.

4. 7

•

Always connect individual members of a shadow set to different K.sdi
boards within the HSC. This hardware configuration rule has the greatest
positive effect on the overall shadow set performance.

•

For write operations, a shadow set suffers only minor performance loss
compared to a single unshadowed disk. Thus, if you are using volume
shadowing primarily for data availability in the event of disk drive failure,
you do not suffer significant performance loss. However, if your primary
goal is to improve data accessibility, the rate of data transfer increases
only in shadow sets with I/O operations that are less than 25% write
operations.

•

For read operations, a two-member shadow set can satisfy nearly twice
as many transfer requests per unit time than a single unshadowed disk.
Three member shadow sets can satisfy nearly 2.5 times as many transfer
requests per unit time as a single unshadowed disk. However, this is
possible only when there are at least as many transfer requests queued
to the shadow set as there are members in the shadow set. You gain no
increased data accessibility by shadowing a disk that never has more than
one request active at a time.

•

Recovering from loss of a shadow set member takes about five to ten
seconds when at least one working member remains in the shadow set.

•

Moving a shadow set from a broken HSC to the alternate working HSC
can take 75 to 120 seconds. It may not take that long, however.

Standalone BACKUP and Volume Shadowing
Because of its very limited system environment, standalone BACKUP
contains no support for shadow sets. The following subsections describe
the limitations for using standalone BACKUP on systems that have shadow
sets, and provide information about how to use standalone BACKUP on
former shadow set members.

4.7.1

lncompatiblities Between Shadow Sets and Standalone BACKUP
DIGITAL does not support accessing shadow sets from standalone BACKUP.
The DIGITAL-supplied command procedures for building standalone
BACKUP kits make every effort to prevent standalone BACKUP from
using volume shadowing improperly. However, these checks can easily
be overridden by a well-informed and sufficiently privileged user.
The following limitations exist for standalone BACKUP on systems that use
volume shadowing:

4-8

•

Do not bootstrap standalone BACKUP from an alternate root on a
shadowed system disk. If you try this, you will crash the system that
is attempting to boot standalone BACKUP.

•

Standalone BACKUP does not configure virtual units. This makes access
to virtual units impossible from standalone BACKUP.

Licensing, Enabling, and Managing VAX Volume Shadowing
4.7 Standalone BACKUP and Volume Shadowing

•

4.7.2

Do not assume that standalone BACKUP prevents you from accessing a
shadow set member unit. You must prevent standalone BACKUP from
sending output to a disk mounted on any other VAXcluster member,
either as a directly accessible disk or as the member of a shadow set.

Using Standalone BACKUP on Disks That Are Former Shadow Set
Members
To use standalone BACKUP on disks that have been members of a shadow
set, you must rebuild your standalone BACKUP console media or alternate
root on your system disk. Your processor installation or operations manual
describes this process.

4.8

Volume Shadowing in Mixed-Interconnect Clusters
As of VMS Version 5.0, you can use VAX Volume Shadowing in a mixedinterconnect VAXcluster configuration which consists of CI-connected
nodes and satellite nodes. Although you can use shadowing with such a
configuration, you must take special precautions described in this section. See
VMS VAXcluster Manual for full information about VAXcluster configurations
and terminology.
If shadowing is to be used anywhere in a mixed-interconnect cluster, all CIconnected VAX nodes must have the SYSGEN parameter SHADOWING set
to 1. This setting causes them to use the shadowing driver, DSDRIVER. The
MSCP Server serves the shadow set virtual unit to the satellites.

Example 4-2 shows how the shadow set appears when you enter the DCL
command SHOW DEVICES D on a boot server. In this example VOYGRl is
the name of an HSC.
Example 4-2
Device
Name
$1$DUA111:
$1$DUA151:
$1$DUS111:

Shadow Set as Seen from Boot Server

(VOYGR1)
(VOYGR1)
(VOYGR1)

Device
Status
ShadowSetMember
ShadowSetMember
Mounted

Error
Count
0
0
0

Volume
Free Trans Mnt
Label
Blocks Count Cnt
(member of $1$DUS111:)
(member of $1$DUS111:)
VMS08JUL
244688
118 21

Satellites must have the SHADOWING parameter set to 0. This setting
causes them to use the non-shadowing driver, DUDRIVER. Satellites access
the shadow set by mounting the virtual unit, and they can see the virtual
unit through the MSCP Server. The shadow set appears to have the same
characteristics as any other disk device, as shown in Example 4-3. However,
while satellites can see shadow set member units, they cannot access them
individually. Iri this example SATURN is the name of the VAX serving the
shadow set.

4-9

Licensing, Enabling, and Managing VAX Volume Shadowing
4.8 Volume Shadowing in Mixed-Interconnect Clusters

Example 4-3
Device
Name
$1$DUA111:
$1$DUA151:
$1$DUS111:

Shadow Set as Seen from Satellite

(SATURN)
(SATURN)
(SATURN)

Device
Status
Online
Online
Mounted

Error
Volume
Free Trans Mnt
Count
Label
Blocks Count Cnt
0 (remote shadow member)
0 (remote shadow member)
244688
121 21
0 VMS08JUL

In mixed-interconnect clusters it is recommended that at least two boot
servers should serve the shadow set, so that if one server should fail, another
is available to keep the shadow set intact.

4.8.1

Mounting Shadow Sets in a Mixed-Interconnect VAXcluster
Configuration
Satellites have no knowlege of shadow set configuration, and they cannot
issue any shadow set maintenance commands using the /SHADOW qualifier.
All commands that create, modify, and dissolve shadow sets must be entered
on a CI-connected node. For example, you must enter a command like the
following on a CI-connected node:
$ MOUNT/CLUSTER $1$DUS111:/SHADOW=($1$DUA111,$1$DUA151) VMS08JUL

This command performs the following operations:

4.8.2

•

Creates the virtual unit and forms the shadow set on the current node

•

Mounts the shadow set on the other CI-connected nodes

•

Mounts the virtual unit on the satellite nodes

Dismounting Shadow Sets in a Mixed-Interconnect VAXcluster
Configuration
Be careful when dismounting shadow sets. The shadow set virtual unit
must always be dismounted on all satellites before being dismounted (and
possibly dissolved) on the CI-connected VAX nodes. If these nodes dismount
the shadow set before satellites do, the shadow set will be dissolved. The
satellites will then have the virtual unit mounted, but will have no path
(through a CI-connected node) to the member units. The satellites will
therefore place the virtual unit in mount verification. This condition can
result in suspended operations, and require a cluster reboot, because satellite~
may hold locks that must be released before the CI-connected node can
rebuild the shadow set.
If this condition occurs, you can remount the shadow set on a CI-connected
serving node. When that node reforms the shadow set, the satellites can ono
again access the volume-provided that the CI-connected node has been abl1
to rebuild the shadow set.

In general, you should use the command DISMOUNT /SYSTEM, rather than
DISMOUNT /CLUSTER, to dismount shadow sets in mixed-interconnect
clusters.

4-10

Licensing, Enabling, and Managing VAX Volume Shadowing
4.8 Volume Shadowing in Mixed-Interconnect Clusters

4.8.3

Using Shadow Sets as Satellite System Disks
A satellite system disk can be a served shadow set. The system device
parameter in the DECnet database for satellites must be the device name of
the shadow set virtual unit (for example, $1$DUS111). No description of
shadow set member units is needed.

4-11

Messages

A.1

Mount Verification Status Messages
Mount verification operations on a shadow set display the following status
messages on the system console, OPAO, and terminals enabled to receive disk
operator messages.

•

<shadow-set-member> : shadow copy has been started.
This indicates the start of a shadow copy operation.

•

<shadow-set-member>: shadow copy has been completed.
This indicates the completion of a shadow copy operation.

•

<virtual-unit> : all shadow set copy operations a.re completed.
This indicates the completion of all pending shadow set copy operations;
all shadow set members contain logical blocks of the same data.

•

<virtual-unit> : shadow set has changed state. Mount verification
in progress.
This indicates a shadow set state change. The size of the shadow set may
be increasing or decreasing. Further messages give details if a change
occurs.

•

<shadow-set-member> : has been removed from shadow set.
This indicates that the specified unit is no longer a member of the shadow
set.

•

<virtual-unit> : shadow set has been reduced.
This indicates the completion of shadow set member removal. Preceding
messages list the removed shadow set members.

•

<shadow-set-member> : is an incorrect shadow set member volume.
This indicates that mount verification has rejected the specified Files-11
shadow set member during a shadow set rebuild. Unless this is the only
available shadow set member, the volume is removed from the shadow
set. The rejected member was probably altered improperly.

•

<virtual-unit> : contains zero working members.
This indicates that mount verification cannot find a working member for
the named shadow set. Subsequent messages name shadow set members
that are not operating. A system operator· must restore one of the named
shadow set members to operational status before MVTIMEOUT (mount
verification timeout) expires; otherwise, mount verification aborts for the
shadow set.

•

<shadow-set-member>: is a possible shadow set member.

A-1

Messages
A.1 Mount Verification Status Messages

This indicates the named shadow set member is a failed member of a
zero-member shadow set. The operator must restore to operational status
this or another named shadow set member before MVTIMEOUT expires;
otherwise, mount verification aborts for the shadow set.

•

<virtual-unit>: does not contain member named to VMB. System
may not reboot.
This indicates that the system disk shadow set member named in the R3
input to VMB is no longer a member of the system disk shadow set. If
this condition exists, mount verification displays this warning message at
the completion of each mount verification operation. Unless you add to
the system disk shadow set the unit named in the R3 input to VMB; the
system may not reboot.

A.2

Mount Verification Messages That Apply to Shadow Sets
In addition to the messages listed previously, the following mount verification
messages can apply to shadow sets. These messages have approximately the
same meaning for shadow sets as they do for regular disks. They are sent to
the system console OPAO and to any operator terminals enabled to receive
disk operator messages.

A.3

•

<virtual-unit> : is offline. Mount verification in progress.

•

<virtual-unit> : has completed mount verification.

•

<virtual-unit> : has aborted mount verification.

MOUNT Messages That Apply to Shadow Sets
The following messages are provided by the VMS Mount Utility or the
$MOUNT system service in response to shadow set operations.
BADSHADOW,

invalid syntax on /SHADOW qualifier

Explanation: The MOUNT command contains an invalid shadow set syntax.
User Action: Correct the syntax and reenter the command, or correct the
program that caused the error.
NOSHDWMEM,

no eligible shadow set members to mount the shadow set

Explanation: There are no valid volumes to create the shadow set. This error
message is followed by the failed status code for each proposed member.
User Action: Examine the status codes, correct the situation, and reenter the
command.

A-2

Messages
A.3 MOUNT Messages That Apply to Shadow Sets

NOTSHDWDEV,

not a shadowing device

Explanation: There are two possible causes for this error message: (1) you
did not use the form DUS or DJS to specify the virtual unit name in the
MOUNT command (in this case the MOUNT command fails), or (2) you
attempted to mount, in a shadow set, a volume that does not support volume
shadowing (for example, a magnetic tape cannot become a shadow set
member).
User Action: Correct the command syntax and enter the command again.
INVSHDWMEM,

shadow set member ddcu: is 'newer' than the shadow set

Explanation: When you attempted to add a volume to an existing shadow
set, the volume to be added had a higher generation number than the shadow
set.
User Action: Determine which volume should be the target of the shadow
copy operation. Re-create the shadow set, and add the target of the copy
operations to it.
SHDWCOPYREQ,

shadow copy required

Explanation: A shadow set member requires a shadow copy operation, but
you specified that no copy operations are allowed.
User Action: Verify that the volume can be initialized (that is, contains no
useful data) and reenter the command allowing shadow copy operations.
SHADOWFAIL,

failed to create (or add to) the shadow set

Explanation: The shadow set cannot be created, or proposed shadow
set members cannot be added to the shadow set. The cause of the failed
operation follows this error message.
User Action: Examine the status code of the failed operation and correct the
error.
SHDWINCVOL,

shadow set member device contains the wrong volume

Explanation: The proposed shadow set member device contains a different
volume than expected. Rather than adding this volume to the shadow set and
initializing it, this volume is not being added to the shadow set.
User Action: Examine this volume and verify that the volume can be
initialized (that is, contains useful data) and reenter the command to add
this volume to the shadow set.
VOLSHDWMEM,

mounting a shadow set member volume; volume write locked

Explanation: This informational message indicates that the volume being
mounted is a former shadow set member. To prevent accidental destruction
of data, this volume is being mounted write-locked.
User Action: To allow write access to this volume, dismount the volume and
remount it with the /OVERRIDE=SHADOW_MEMBERSHIP qualifier.

A-3

Messages
A.3 MOUNT Messages That Apply to Shadow Sets

SHDWMEMSUCC,

ddcu: is now a valid member of the shadow set

Explanation: This informational message indicates that device ddcu: is a f
shadow set member.
User Action: None.
SHDWMEMCOPY,

ddcu: added to the shadow set with a copy operation

Explanation: This informational message indicates that device ddcu: is bei
added to the shadow set with a copy operation. When the copy operation
complete, the device is a full shadow set member.
User Action: None.
SHDWMEMFAIL,

ddcu: failed as a member of the shadow set

Explanation: This informational message indicates that device ddcu: cann
be made a shadow set member. The failure status code follows this messa~
User Action: Examine the failure status codes, correct the situation, and
reenter the command.

A-4

MOUNT Qualifiers for Volume Shadowing

This appendix presents the MOUNT command qualifiers that you can use
with VAX Volume Shadowing. This material is presented to allow insertion
into the VMS Moun_t Utility Manual.

B-1

MOUNT Qualifiers for Volume Shadowing
/CONFIRM

/CONFIRM
Controls whether the Mount Utility (MOUNT) issues a request to confirm
a full copy operation when mounting a shadow set. The default is
/NOCONFIRM.

FORMAT

/CONFIRM

DESCRIPTION

You can specify /CONFIRM as a precaution to avoid erasing important
data during full copy operations. /CONFIRM stops automatic copying
of targeted potential shadow set members. When you mount or add to a
shadow set, members that contain data less current than that in other shadov
set members are targets for full copy operations. Unless you specify the
/CONFIRM or the /NOCOPY qualifier, MOUNT automatically overwrites
the data of the targeted volumes.

virtual-unit-name[:]
/SHADOW=(physical-device-name[:}[, ... l
/NOCONFIRM virtual-unit-name[:} /SHADOW=
(physical-device-name[.}[, ... ])

The MOUNT /CONFIRM command displays the volume label and volume
owner for any specified physical device that requires a full copy operation.
MOUNT then stops the full copy operation and displays the following
prompt:
Allow FULL shadow copy on the above member(s)? [NJ:

Section 2.1.4.3 of the VAX Volume Shadowing Manual describes how MOUN1
determines the sources and targets of shadow set copy operations. In brief,
the shadow set member with the most current volume shadowing generation
number is the source for copy operations to potential shadow set members.
Other potential shadow set members must have been marked with identical
generation numbers or they are targets for full copy operations.
The /CONFIRM qualifier is similar to the /NOCOPY qualifier except that
with /NOCOPY there is no interactive exchange. /NOCOPY also terminate~
the mount operation if there are any potential full copy operations. Use
/CONFIRM to mount a shadow set interactively, and use /NOCOPY
to mount shadow sets in the site-specific startup command procedure
SYS$MANAGER:SYSTARTUP.COM. (See the /NOCOPY qualifier for
information about using it with a system disk shadow set.)

B-2

MOUNT Qualifiers for Volume Shadowing
/CONFIRM

EXAMPLES
iJ

$ MOUNT/CONFIRM DUS23: /SHADOW=($1$DUA4: ,$1$DUA6:) SHADOWVOLCt
%MOUNT-F-SHDWCOPYREQ, shadow copy required
Virtual Unit - $1$DUS23 (HSC001)
Volume Label - SHADOWVOLf)
Member
Volume Label Owner UIC8
$1$DUA6: (LOVE)
SCRATCH
[100,100]
Allow FULL shadow copy on the above member(s)? [NJ: NOC)
$

This example shows how to use the /CONFIRM qualifier to check the status
of potential shadow set members before any data is erased.

Ct This command instructs MOUNT to build a shadow set, with the specified
devices, and prompt for permission to perform any full copy operations.

Because a full copy operation is necessary, the virtual unit name and the
volume label is displayed.

The display also includes the physical device name, the volume label, and
the volume owner of the potential shadow set member that requires the
copy operation.

A response of NO instructs MOUNT to quit with no mounting or
copying.

$ MOUNT/CONFIRM DUS23: /SHADOW=($1$DUA4: ,$1$DUA6:) SHADOWVOL
%MOUNT-F-SHDWCOPYREQ, shadow copy required
Virtual Unit - $1$DUS23 (HSC001)
Volume Label - SHADOWVOL
Member
Volume Label Owner UIC
$1$DUA6: (LOVE)
SCRATCH
[100,100]
Allow FULL shadow copy on the above member(s)? [NJ: YES
%MOUNT-I-SHDWMEMSUCC, _$1$DUA4: (HSC001) is now a valid member of the
shadow set
%MOUNT-I-SHDWMEMCOPY, _$1$DUA6: (HSC001) added to the shadow set with
a copy operation
$

This example shows how to use the /CONFIRM qualifier to check the status
of potential shadow set members before any data is erased. A response of
YES to the prompt instructs MOUNT to form the shadow set with a full copy
operation.

B-3

MOUNT Qualifiers for Volume Shadowing
/COPY

/COPY
Enables or disables copy operations on physical devices named when
mounting or adding to a shadow set. The default is /COPY.

FORMAT

virtual-unit-name[:]
/SHADOW=(physical-device-name[:j[,
])
/NOCOPY virtual-unit-name[:]
/SHADOW=(physical-device-name[:j[, ... ])

DESCRIPTION

/COPY

A MOUNT /NOCOPY operation fails if any of the specified potential shadow
set members require full copy operations. Error messages identify the targets
of full copy operations. If the targets of full copy operations are as expected,
you can mount the shadow set with the /COPY qualifier. If not, you have
not lost data, and should enter a new command that specifies units that can
be overwritten.
Section 2.1.4.3 of the VAX Volume Shadowing Manual describes how MOUNT
determines the sources and targets for shadow set copy operations. In brief,
the shadow set member with the most current volume shadowing generation
number is the source for copy operations to potential shadow set members.
Other potential shadow set members must have been marked with identical
generation numbers or they are targets for full copy operations.
The /NOCOPY qualifier is similar to the /CONFIRM qualifier except that
with /CONFIRM there is an interactive exchange in which you can continue
a mount with copy operations. Use /CONFIRM to mount a shadow set
interactively, and /NOCOPY to mount shadow sets in the site-specific
startup command procedure SYS$MANAGER:SYSTARTUP.COM. (Using the
/NOCOPY qualifier with a system disk shadow set either has no effect, as
in the case where the system boots from a virtual unit, or causes the mount
operation to fail, which is not generally useful for a system disk.)
The /NOCOPY qualifier guards against accidental destruction of data when
the system reboots and forms a shadow set using incorrect volumes (caused
by different volumes being put into the drives or drive unit plugs being
accidentally switched when the system is down).

B-4

MOUNT Qualifiers for Volume Shadowing
/COPY

EXAMPLE
$ MOUNT/NOCOPY DUS2: /SHADOW=($1$DUA4: ,$1$DUA6: ,$1$DUA7:) _$ SHADOWVOL DISK$SHADOWVOL0
%MOUNT-F-SHDWCOPYREQ, shadow copy required
%MOUNT-I-SHDWMEMFAIL, DUA7: failed as a member of the shadow set
%MOUNT-F-SHDWCOPYREQ, shadow copy requiredf.)
$ MOUNT/COPY DUS2: /SHADOW=($1$DUA4: ,$1$DUA6: ,$1$DUA7:) _$ SHADOWVOL DISK$SHADOWVOL8
%MOUNT-I-MOUNTED, SHADOWVOL
mounted on _$1$DUS2: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA4: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMSUCC, _$1$DUA6: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMCOPY, _$1$DUA7: (HSC001) added to the shadow set
with a copy operationO

This example shows how to use the /NOCOPY qualifier to check the status
of potential shadow set members before any data is erased.

This command instructs MOUNT to build a shadow set, with the specified
devices, only if no copy operations are required.

f.)

This command instructs MOUNT to build a shadow set providing the
necessary copy operations.

The shadow set is mounted. The volume in device $1$DUA7 receives a
full copy operation.

B-5

MOUNT Qualifiers for Volume Shadowing
/OVERRIDE

/OVERRIDE
Inhibits one or more protection checks performed by the MOUNT
command.

FORMAT
QUALIFIER
VALUE

/OVERRIDE=(option[, ... ])

device-name:

option
The following protection check option is available for mounting disks
formerly mounted in a Files-11 shadow set.

SHADOW_MEMBERSHIP
Disks that have been mounted as shadow set members on a system can use
the volume shadowing option. Use /OVERRIDE=SHADOW_MEMBERSHIP
to mount a former shadow set member for write operations outside of a
shadow set. If you do not use /OVERRIDE=SHADOW_MEMBERSHIP,
MOUNT automatically mounts the volume write-locked to prevent accidental
alteration of data.
When you use this qualifier, the shadow set generation number is erased
from the volume. If you then remount the volume in the former shadow
set, MOUNT considers it an unrelated volume and marks it for a full copy
operation.
To use /OVERRIDE=SHADOW_MEMBERSHIP, you must have VOLPRO
privilege or your UIC must match the owner UIC of the volume.

Note: DIGITAL recommends that you do not mount a shadow set with the
/OVERRIDE=IDENTIFICA TION qualifier; see Section 2.1.5.4 of the VAX
Volume Shadowing Manual for details.

EXAMPLE
$ MOUNT/OVERRIDE=SHADOW_MEMBERSHIP $4$DUA20: WORKDISK

This command overrides the write protection and erases the volume
shadowing generation number field, thus mounting a former shadow set
member on $4$DUA20.

B-6

MOUNT Qualifiers for Volume Shadowing
/SHADOW

/SHADOW
Directs the Mount Utility to bind the specified physical devices into a
shadow set represented by the specified virtual unit.

FORMAT

QUALIFIER
VALUES

virtual-unit-name[.}/SHADOW=
(physical-device-name[:}[, ... ])
virtual-unit-name[:]
The required name for the software representation of a shadow set. Use the
virtual unit naming formats [$allocation-class$]ddSu[:] or [hsc$]ddSu[:].

If the allocation class is not zero, use the allocation class format. If you
omit the HSC name or allocation class when you specify a virtual unit in a
VAXcluster, MOUNT substitutes the HSC name or allocation class of the most
current shadow set member.
The dd describes the device type of the physical devices used, S identifies the
unit as a shadow set, and u is a unique number from 0 through 9999.

physical-device-name[:][, ... ]
The name of a disk drive that contains a disk to be mounted in a shadow
set. If you specify only one device, you can omit the parentheses. Use the
standard HSC-mounted device naming formats $allocation-class$ddcu[:] or
hsc$ddcu[:]. If your devices are dual ported to HSCs, use the $allocationclass$ddcu[:] format. A named disk becomes a shadow set member
represented by the virtual unit.

DESCRIPTION

Use the /SHADOW qualifer to mount a shadow set or a volume set of
shadow sets. You must specify at least one physical device. If you specify
more than one physical device, more current Files-11 disks are copied to less
current Files-11 disks by default. To disable the copy operations, use the
/NOCOPY qualifier. If you are mounting a shadow set interactively, you
can use the /CONFIRM qualifier. /CONFIRM instructs MOUNT to display
the targets of copy operations and request permission before the copies are
performed.
Foreign volumes require special treatment to be mounted in a shadow set.
When you mount a foreign shadow set, you must specify the desired copy
operation: FULL _COPY=ddcu, MERGE_COPY=ddcu, or NO_COPY=ddcu
for each physical device you list with the /SHADOW qualifier. See the VAX

Volume Shadowing Manual.

B-7

MOUNT Qualifiers for Volume Shadowing
/SHADOW

EXAMPLE
$MOUNT DUSO: /SHADOW=($1$DUA10: ,$1$DUA11:) SHADOWDISK
%MOUNT-I-MOUNTED, SHADOWDISK
mounted on _$1$DUSO: (HSC001)
%MOUNT-I-SHDWMEMSUCC, _$1$DUA10: (HSC001) is now a valid member of
the shadow set
%MOUNT-I-SHDWMEMCOPY, _$1$DUA11: (HSC001) added to the shadow set
with a copy operation

This example shows how to create a Files-11 shadow set wherein the
software determines automatically the correct copy operation for the two
shadow set members. MOUNT checks the volume shadowing generation
numbers on the volumes, selects the more current shadow set member, and
performs the appropriate copy operation. In this example, $1$DUA10 is
the more current volume and becomes the source of the copy operation to
$1$DUA11.

B-8

System Services Item Codes for Volume
Shadowing
This appendix presents the $GETDVI and $MOUNT system service item
codes that you can use with VAX Volume Shadowing. This material is
presented to allow insertion into the descriptions of the $GETDVI and
$MOUNT system services contained in the VMS System Services Reference

Manual.

C-1

System Services Item Codes for Volume Shadowing

$GETDVI Volume Shadowing Item Codes
DVl$_SHDW_CATCHUP_COPYING
When you specify DVl$_SHDW_CATCHUP_COPYING, $GETDVI returns
a longword, which is interpreted as Boolean. The value 1 indicates that the
device is a member receiving a full copy operation before joining a shadow
set.
DVl$_SHDW_FAILED_MEMBER
When you specify DVl$_SHDW_FAILED_MEMBER, $GETDVI returns a
longword, which is interpreted as Boolean. The value 1 indicates that the
device is a member that has been removed from the shadow set by the
remote server.
DVl$_SHDW_MASTER
When you specify DVl$_SHDW_MASTER, $GETDVI returns a longword,
which is interpreted as Boolean. The value 1 indicates that the device is a
virtual unit.
DVl$_SHDW_MASTER_NAME
When you specify DVl$_SHDW_MASTER_NAME and the specified device
is a shadow set member, $GETDVI returns the device name of the virtual un
that represents the shadow set of which the specified device is a member.
$GETDVI returns a null string if the specified device is not a member or is
itself a virtual unit.

When the shadow set members are dual-pathed to two HSCs and therefore
have a nonzero allocation class, the device name returned by $GETDVI
contains the allocation class; the name has the form $allocation-class$devic1
For example, if a virtual unit has an allocation class of 255 and the device
name DUSlO, $GETDVI returns the following string: $255$DUS10.
When the shadow set members have a zero allocation class, the device
name contains the HSC node name; the name has the form hsc$device. For
example, if the node name of the HSC -is LAMONT and the device name is
DUSlO, $GETDVI returns the following string: LAMONT$DUS10.
Because the shadow set virtual unit name can include up to 64 characters, th
buffer length field of the item descriptor should specify 64 (bytes).
DVl$_SHDW_MEMBER
When you specify DVl$_SHDW_MEMBER, $GETDVI returns a longword,
which is interpreted as Boolean. The value 1 indicates that the device is a
shadow set member.
DVl$_SHDW_MERGE_CQPYING
When you specify DVl$_SHDW_MERGE_COPYING, $GETDVI returns a
longword, which is interpreted as Boolean. The value 1 indicates that the
device is a member receiving a merge copy operation before joining a shado'
set.
DVl$_SHDW_NEXT_MBR_NAME
When you specify DVl$_SHDW_NEXT_MBR_NAME, $GETDVI returns th1
device name of the next member in the shadow set. If you specify a virtual
unit, $GETDVI returns the device name of the lowest-numbered member.
If you specify a member, $GETDVI returns the device name of the member

C-2

System Services Item Codes for Volume Shadowing

with the next highest number. If you specify the device name of the highestnumbered member, $GETDVI returns a null string. If you specify the name
of a device that is neither a virtual unit nor a member, $GETDVI returns a
null string.
$GETDVI returns the device name of the next member in the shadow set
even if the remote server has removed the next member from the shadow set.
When the shadow set members are dual pathed to two HSCs and therefore
have a nonzero allocation class, the device name returned by $GETDVI
contains the allocation class; the name has the form $allocation-class$device.
For example, if a shadow set has an allocation class of 255 and the device
name is DUSlO, $GETDVI returns the following string: $255$DUS10.
When the shadow set members have a zero allocation class, the device
name contains the HSC node name; the name has the form hsc$device. For
example, if the node name of the HSC is LAMONT and the device name is
DUSlO, $GETDVI returns the following string: LAMONT$DUS10.
Because a device name can include up to 64 characters, the buffer length field
of the item descriptor should specify 64 (bytes).

C-3

System Services Item Codes for Volume Shadowing

$MOUNT Volume Shadowing Item Codes
MNT$_SHANAM
The MNT$_SHANAM item code specifies the name of the virtual unit to be
mounted. The buffer must contain a character string from 1 to 64 characters,
which is the virtual unit name. The virtual unit name may be a logical name
if it is a logical name, it must translate to a virtual unit name. The name
should include the controller letter S, which indicates that the device is a
virtual unit.
Because every shadow set is represented by a virtual unit, you must include
at least one MNT$_SHANAM item descriptor in the item list that you pass
to $MOUNT to create and mount the shadow set. If you are mounting a
Files-11 volume set containing more than one shadow set, you must include
one MNT$_SHANAM item descriptor for each virtual unit included in the
volume set.
The relative position of the item descriptors in the item list determines the
membership of the shadow set. That is, it indicates which members should
be bound to a specific virtual unit to form the shadow set. You must first
specify the virtual unit by using the MNT$_SHANAM item code. Then,
you can specify any number of members that are to be represented by that
virtual unit by using one of the following item codes: MNT$_SHAMEM,
MNT$_SHAMEM_MGCOPY, or MNT$_SHAMEM_COPY. If you specify
one shadow set and want to specify a second, specify second virtual unit
item descriptor. The members you specify subsequently are bound to the
shadow set represented by the virtual unit specified in the second virtual uni·
item descriptor.

MNT$_SHAMEM
The MNT$_SHAMEM item code specifies the name of a member (physical
device) to be added to the shadow set represented by the most recently
specified virtual unit, that is, the virtual unit name specified in the most
recent MNT$_SHANAM item descriptor. The buffer must contain a characte
string from 1 to 64 characters, which is the device name. The device name
may be a physical device name or a logical name; if it is a logical name, it
must translate to a physical device name.
If you are mounting a foreign shadow set, the MNT$_SHAMEM item code
indicates that the member specified in the item descriptor does not require a
shadow copy before it joins the shadow set.

When you mount a foreign shadow set, the system considers the first membe
you specify after the virtual unit item descriptor to be the most current
member of the shadow set. The system makes copies to other members basec
on this member. You must use the MNT$_SHAMEM item code to specify
the first member of a foreign shadow set, because it can never require a copy
operation before joining the shadow set.
To be valid, an item list must contain at least one item descriptor specifying
a member; this item descriptor must appear after the MNT$_SHANAM item
descriptor.

C-4

System Services Item Codes for Volume Shadowing

a physical device name or a logical name; if it is a logical name, it must
translate to a physical device name.
When mounting a foreign shadow set, use the MNT$_SHAMEM_COPY item
code to indicate that the member specified in the item descriptor requires a
full copy operation before it can join the shadow set.
MNT$_SHAMEM_MGCOPY
The MNT$_SHAMEM_MGCOPY item code specifies the name of a member
to be added to the shadow set represented by the most recently specified
virtual unit, that is, the virtual unit specified in the most recent MNT$_
SHANAM item descriptor. The buffer must contain a character string from
1 to 64 characters, which is the device name. The device name may be
a physical device name or a logical name; if it is a logical name, it must
translate to a physical device name.

When mounting a foreign shadow set, use the MNT$_SHAMEM_MGCOPY
item code to indicate that the member specified in the item descriptor requires
a merge copy operation before it can join the shadow set.
MNT$_FLAGS
The MNT$_FLAGS item code specifies a longword bit vector wherein each
bit specifies an option for the mount operation. The buffer must contain a
longword, which is the bit vector.

The $MNTDEF macro defines symbolic names for each option (bit) in the bit
vector. You construct the bit vector by specifying the symbolic names for the
desired options in a logical OR operation. The following table describes the
symbolic names for each shadow set option.
Option

Description

MNT$V_NOCOPY

C-5

System Services Item Codes for Volume Shadowing

Option

Description

MNT$V_OVR_SHAMEM

Allows you to mount former shadow set members
outside of the shadow set. If you do not specify this
option, $MOUNT automatically mounts the volume
write-locked to prevent accidental deletion of data.
To specify this option, you must either own the
volume or have VOLPRO privilege.
When you use this option, the shadow set generation
number is erased from the volume. If you then
remount the volume in the former shadow set,
$MOUNT considers it an unrelated volume and marks
it for a full copy operation.

C-6

Index

Allocation class• 1-2
physical unit• 2-3
virtual unit• 2-2

Backup operation• 2-18 to 2-22
shadow copy as• 2-18
VMS Backup Utility• 2-19 to 2-22
Backup Utility (BACKUP)
/IMAGE qualifier• 2-20
revision number• 2-20
used for Files-11 copy operation• 2-7
standalone
restrictions. 4-8
with former shadow set members• 4-9

Data Compression/Expansion (DCX)
routines• 2-22
DEFBOO.CMD • 4-3
upgrade• 4-5
Device name
Files-11 format• 2-3
Disk drive
compatibility for volume shadowing• 1-3
Dismount
in mixed-interconnect V AXcluster configuration
•4-10
proper
used for Files-11 copy operation• 2-7
DISMOUNT command
shadow set member• 2-12
overview• 1-9
virtual unit• 2-13
overview• 1-9

Configuration, system
performance• 4-8
/CONFIRM qualifier• 2-8 to 2-9
Copy operation

Error message• A-1 to A-4
MOUNT•A-2
mount verification• A-1

See also /CONFIRM qualifier
See also /COPY qualifier
Files-11 volume• 2-6 to 2-7
BACKUP revision number• 2-7
determining correct• 2-6 to 2-7
example• 2-7
proper dismount• 2-7
volume label• 2-6
volume shadowing generation number• 2-7
/COPY qualifier• 2-9 to 2-10
Copy-type specifier
foreign shadow set• 2-4

F
F$GETDVI lexical function• 2-17 to 2-18
item names• 2-17
Full copy operation
Files-11 shadow set• 2-6
FULL _COPY specifier
foreign shadow set• 2-5

H
Hardware requirement• 1-3 to 1-6

lndex-1

Index

Hierarchical Storage Controller
See HSC
HSC (Hierarchical Storage Controller)• 1-2

I
Installation
See License registration
Item codes
used with SYS$GETDVI • 3-11
used with SYS$MOUNT • 3-2

L
License registration
for volume shadowing• 4-1 to 4-2
Logical-name parameter• 2-3

M
Mass Storage Control Protocol
See MSCP
Merge copy operation
shadow set• 2-6
MERGE_COPY specifier
foreign shadow set• 2-5
Message• A-1 to A-4
MOUNT•A-2
Mixed-Interconnect V AXcluster
configuration • 4-9 to 4-11
Mount
in mixed-interconnect V AXcluster
configuration• 4-10
MOUNT command
messages• A-2
Mount verification• 1-2
messages• A-1
MSCP (Mass Storage Control Protocol)• 1-2

N
/NOMOUNL VERIFICATION qualifier• 2-11
NO_COPY specifier
foreign shadow set• 2-5

lndex-2·

0
/OVERRIDE=IDENTIFICA TION qualifier• 2-11
/OVERRIDE=SHADOW _MEMBERSHIP
qualifier• 2-10 to 2-11

p
Performance
on systems with volume shadowing• 4-8
Physical unit
allocation class name• 2-3
HSC name• 2-3
Product Authorization Key (PAK)
registering• 4-1 to 4-2

a
Qualifier
/CONFIRM• 2-8 to 2-9
/COPY•2-9to 2-10
/NOMOUNL VERIFICATION• 2-11
/OVERRIDE=IDENTIFICATION • 2-11
/OVERRIDE=SHADOW _MEMBERSHIP•
2-10to 2-11
Qualifier list• 2-1 to 2-2
Quorum disk• 1-10

R
Remote server• 1-2

s
/SHADOW qualifier• 2-1
Files-11 • 2-3
Shadow set• 1-2
adding member to• 2-11
as a system disk• 4-2
overview • 1--1 0
changes• 1-7
creating• 2-1

Index

Shadow set
creating (cont'd.)
Files-11 • 2-2 to 2-4
foreign• 2-4 to 2-5
with SYS$MOUNT • 3-1 to 3-7
dismounting• 2-13
overview• 1-9
SYS$DISMOU example• 3-10
with SYS$DISMOU • 3-10
dissolving• 2-13
overview • 1-9
SYS$DISMOU example• 3-10
with SYS$DISMOU • 3-10
examining• 2-14 to 2-18
overview• 1-8
examples
Files-11 • 2-4
Files-11
copy operations• 2-6 to 2-7
full copy operation• 2-6
merge copy operation• 2-6
foreign• 2-4 to 2-5
copy-type specifiers• 2-4
example• 2-5
FULL_COPY specifier• 2-5
MERGE_COPY specifier• 2-5
NO_COPY specifier• 2-5
in a V AXcluster
overview • 1-10
maintaining• 2-22
mounting • 1-6
with SYS$MOUNT • 3-1 to 3-7
mounting Files-11
SYS$MOUNT example• 3-5
mounting Files-11 volume set
SYS$MOUNT example• 3-6
mounting foreign
SYS$MOUNT example• 3-7
processing shadow set member• 2-22
quorum disk• 1-10
removing member unit• 2-12
SYS$DISMOU example• 3-9
standalone BACKUP• 4-8
system disk
booting• 4-3
upgrade• 4-5
using VMS Data Compression/Expansion (DCX)
routines• 2-22
Shadow set member• 1-2
adding• 2-11
overview• 1-9
initializing• 1-7

Shadow set member (cont'd.)
mounting former• 2-10
removing• 2-12
overview• 1-9
standalone BACKUP with former• 4-9
Shadow set state change• 1-2
SHOW DEVICES command• 2-14 to 2-16
examples• 2-15
overview• 1-8
shadow set member• 2-14
virtual unit• 2-14
with a mixed-interconnect V AXcluster
configuration• 4-9
Standalone BACKUP
restrictions• 4-8
with former shadow set members• 4-9
SYS$DISMOU
condition values returned by• 3-8
dismounting volumes with• 3-8 to 3-11
SYS$GETDVI
getting information about volumes
with • 3-11 to 3- 13
SYS$MOUNT
condition values returned by• 3-8
mounting volumes using• 3-1 to 3-7
shadow set item codes• 3-2
SYS$010
condition values returned by• 3-8
SYST ARTUP_ V5 .COM• 4-3
System configuration• 1-3 to 1-6
performance• 4-8
System disk shadow set• 4-2
booting from • 4-3
upgrade• 4-5
System Generation Utility (SYSGEN) • 4-2
setting the SHADOWING parameter• 4-2
SHADOWING parameter
on Cl-connected nodes in mixedinterconnect V AXcluster
configuration• 4-9
on satellite nodes in mixed-interconnect
V AXcluster configuration• 4-9
System services
performing shadow set
operations• 3-1 to 3-1 3

T
Terms for volume shadowing• 1-2 to 1-3

lndex-3

Index

u
Unit number
depositing• 4-3
Upgrade
on a system disk shadow set• 4-5

v
Virtual unit• 1-3
allocation class name• 2-2
device type• 2-2

HSC name• 2-2
number• 2-2
S identifier• 2-2
VMS.EXE• 4-2
Volume
compatibility• 1-3
Volume label
parameter• 2-3
used for Files-11 copy operation• 2-6
Volume shadowing generation number
erasing• 2-10
used for Files-11 copy operation• 2-7

w
Write protection
hardware• 1-4
override • 2-10

lndex-4

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VAX Volume Shadowing
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AA-LB 18A-TE

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