The ALOG file enables you to recover critical tape data in case of a VMF failure. The ALOG file is a critical part of VMF recovery processing. You should back up the ALOG file on a daily basis, or more frequently, if the volume of tape processing is very high. The ALOG file is used to record the individual transactions applied to the VMF and is similar to a database journal or log file. The CATALOGB procedure is provided to back up the ALOG transactions to tape.
The ALOG file is reset each time you run the CATALOGB procedure, only the transactions created since the last time CATALOGB was run will be written to the ALOG backup tape.
CA TLMS r12.6
Retaining ALOG backups helps you recover all the tape data in case the VMF is lost or damaged and provides you an audit trail to determine what has happened to a volume over time. We recommend that you retain VMF and ALOG backups for six - twelve months. These backups allow you to go back in time to research detailed activity for tape volumes. If you find that a tape has been scratched or modified and you need to understand what has happened, the ALOG data will provide the answer. The ALOG records show all the updates to the VMF from real-time Open/Close/EOV events, batch jobs, and CATLTP updates.
You can use IEBGENER to concatenate the daily ALOG backup tapes onto fewer tapes. Using this method, you can create a weekly or a monthly tape instead of individual daily ALOG tapes. As is the case when using multiple ALOG files as input, they should always be processed in the order OLDEST to NEWEST.