The Recovery Order

Tips and techniques for implementing the BRMS recovery policy

Currently, BRMS Recovery restores libraries in order by save date, save time, and library name.

With the September 2019 PTFs, the STRRCYBRM command now orders *IBM and *ALLUSR libraries by ascending tape sequence order.

Compare these examples for reference:

Current SORT(*SIZE) behavior

When using SORT(*SIZE) in a backup policy or control group, and multiple libraries are saved with the same save date and timestamp, BRMS Recovery will restore those libraries in alphabetical order instead of the order in which they were saved. This situation affects performance and increases recovery time because it requires the tape drive to rewind and reposition between each library restoration.

Example using alphabetical sort order

Example of recovery processing using the standard behaviors


New SORT(*SIZE) behavior

Starting with the September 2019 BRMS PTFs (7.2 – SI70624, 7.3 SI70625, 7.4 - SI70626), BRMS has enhanced the recovery processing to sort libraries by tape sequence for each volume.

Example with September 2019 BRMS PTF enhancement

The new method BRMS uses to sort libraries for recovery

The recovery list in this example shows how the saved items are listed in tape sequence order. This eliminates tape device rewind and repositioning between each library restore, thus improving the restore performance. Using this method not only fixes the handling of SORT(*SIZE) backups, but any situation where sequence numbers were out of order previously.


Considerations:

Sorting by sequence numbers is applied only to *IBM and *ALLUSR libraries.