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XX-E0797-CD

September 2003

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Document:	AN-028
Order Number:	XX-E0797-CD
Revision:	0
Pages:	1
Original Filename:	AN-028.pdf

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CHARON-VAX application note
AN-028 Avoiding CHARON disk timeout messages in Windows/XP
Author:

Software Resources International

Applies to:

All CHARON-VAX versions using disk images

Host OS:

Windows XP Professional

Date: 16 Sept 2003

VMS 'disk offline' error
Windows XP has the "System Restore" function enabled by default. This function will
checkpoint files with specific extensions at certain events, to restore a recent version of the
file in case of system malfunction. Other versions of Windows can enable this function.
The default file extension of disk images in the current releases of CHARON-VAX is .dsk, an
extension on which the Windows system restore function operates by default. The result is
that at the start of CHARON-VAX such a restore operation might be initiated, which has been
measured taking 40 seconds or more for a large diks.dsk container file. Since VMS has no full
speed access to the file during a system restore and considers that a disk is offline if it was not
accessible during 6 seconds, a VMS 'disk offline' error might occur. The chance that this
event happens appears to increase with increasing host system CPU frequency.

Workaround
There are several ways to disable a system restore for all CHARON-VAX disk images. Since
the CHARON-VAX ODS2 disk image format is not understood by Windows, a restore
operation by Windows is not appropriate for these disk images in any case:
1. Turn off the Windows system restore function system wide or for the volume containing
the CHARON-VAX disk images (Control Panel | System | System Restore)
2. Modify the %windir%\system32\restore\Filelist.xml file, which specifies the files &
directories monitored by the Windows system restore function.
3. Change the extension of your .dsk file to an extension which is not monitored by default
(for instance *.vdisk) and adapt your configuration file accordingly.
Future releases of the CHARON emulators will use the *.vdisk extension instead in
documentation, configuration files and examples.
Note that journaling enabled on the volume containing the disk images might cause a similar
disk offline problem, and should be disabled in case of problems.
[30-18-028]

©2003 Software Resources International. This document is provided for information only and is not a legally binding offer.
Software Resources International reserves the right to change the product specifications without prior notice or retire the
product. The CHARON name and its logo are a registered trademark of Software Resources International. For further
information: www.charon-vax.com, Email: vaxinfo@vaxemulator.com