Record distribution and the partition selection exit routine

If you use a partition selection exit routine, the distribution of records across partitions is managed by the exit routine, not by IMS.

To adjust the distribution of records across partitions, you must modify the exit routine.

IMS cannot detect changes in the exit routine to the distribution of records. Nor does IMS know which partitions are affected by those changes. Consequently, you must understand which partitions are affected by any changes you make and initialize them accordingly.

When a change causes records to be moved from one partition to another, you must run the HD Reorganization Unload utility (DFSURGU0), set the partition-initialization-required (PINIT) flags, initialize, and run the HD Reorganization Reload utility (DFSURGL0) for every partition that is affected by the movement of records.

You should also ensure that any partition selection exit routine that you are using contains code that processes the structure initialization and structure modification calls that IMS issues when updating online partition structures after partitions are added or modified. The sample Partition Selection exit routine (DFSPSE00) provided with IMS includes code that supports these calls.