HP Volume Shadowing for OpenVMS

This document is the "HP Volume Shadowing for OpenVMS OpenVMS Version 8.4" manual, published in June 2010.

It explains how to use HP Volume Shadowing (also known as disk mirroring) on OpenVMS Integrity servers and OpenVMS Alpha systems to:

• Achieve high data availability and redundancy by transparently replicating data across multiple disks, preventing single points of failure.
• Configure and manage shadow sets, which are logical groupings of one to six physical disks presented as a single virtual unit to applications and users.
• Understand and control various operations like mount, copy, assisted copy, minicopy, merge, and minimerge, which maintain data consistency during changes in shadow set membership or system failures.
• Perform system management tasks on shadowed systems, including operating system upgrades, backup operations (leveraging minicopy for efficiency), and crash dumping.
• Optimize performance of shadow sets by understanding factors that affect I/O, resource utilization, and by adjusting system parameters like SHADOW_MAX_COPY and SHADOW_REC_DLY.
• Utilize Host-Based Minimerge (HBMM), a feature introduced in later OpenVMS versions, to significantly reduce merge times using write bitmaps and policies.
• Interpret various system messages related to volume shadowing.

The manual is intended for system managers and users familiar with the OpenVMS operating system, Mount utility, system services, and parameter settings. It details command-line interface (DCL) commands and system services for managing shadow sets and also covers hardware environment requirements and licensing. It explicitly states that Volume Shadowing for OpenVMS is host-based only since OpenVMS Version 6.2.