Online ACB library cut over – IMS Contention Issue

Problem:

Planning for high availability change. There was only a new PSB to be defined as part of a release. NEW PSB can be defined in IMS region dynamically. During a high available release, the PSB gen was generated for the NEW PSB alone, but the ACB was built with BUILD ALL.  So during modify prepare and commit it was giving lots of the contentions as it was trying to refresh all ACB members.

Reason:

The modify commit will not be successful as all members of the ACBLIB was considered as changed.  Only we had 2 options, bring down all MPP region and IMS Databases down to complete the online ACB flip or reset everything and fix the ACB library. We decided to do the second one as it was better option in this case.

Solution:

Copy all the members from active ACBLIB library to the ACBLIB and inactive ACBLIB library. To bring back the ACB library to original status and then redo the ACB build with build for the new PSB alone.

Lessons Learnt:

ACB built should be for the only the new or changed member alone for a high availability release. ACB Build all is need only during IMS version upgrade or a major outage release when many members are impacted.