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IBM® Virtualization Engine TS7700 Series Best Practices - Return-to-Scratch Considerations for Disaster Recovery Testing with a TS7700 Grid V1.2

Document Author:
Additional Author(s):

Parker Wall
Jane P Riddle

Document ID:


Doc. Organization:

IBM Systems

Document Revised:


Product(s) covered:

# 3956; # 3957; # 3957-V06; Virtualization Engine; Virtualization Engine TS7700

Abstract: When performing disaster recovery (DR) testing with a TS7700 grid, you need to consider how to handle Return-To-Scratch (RTS) processing by a production host.

The DR host uses a snapshot of the production host’s tape catalog. This allows the production host to continue its processing without affecting the DR test. Also, typically, a special range of DR volumes are inserted into the DR TS7700 for use as scratch volumes by the DR host.

During the DR test, the DR host needs to be able to mount volumes that are private according to the tape catalog snapshot. You want to avoid the production host overwriting a volume that it has returned to scratch during the DR test period. Overwriting occurs if the scratched volume subsequently gets selected for a mount.

The cleanest method to deal with RTS processing is to suspend it during the DR test. This way the production host will not return a volume to scratch, and then have it selected for a mount, and subsequently overwrite the data on the tape. If you suspend RTS processing during the DR test, you will need to ensure there are sufficient scratch volumes for use by the production host for the duration of the DR test.

However, it isn’t always practical to suspend Return-To-Scratch (RTS) processing. This paper helps you to understand scratch selection criteria used by both the pre-Release 1.5 and Release 1.5 TS7700. With this knowledge, you will be able to plan for your DR test whilst RTS processing is kept active.

This paper also addresses other scratch category considerations for a DR test. These include the fast-ready and Expire-Hold attributes for a scratch category.

Our recommendations are summarized at the end of this paper.

White Paper - TS7700 Best Practices - Return-To-Scratch Considerations for DR Testing V12.pdf




Operational Management





TS7700, 7700, TS7740, 7740, TS7720, 7720, Virtualization Engine

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