Enqueue Installation Exit Routine (ADRUENQ)

The enqueue installation exits routine that is supplied with DFSMSdss passes a return code of zero. This causes DFSMSdss to do the following:

For a full or tracks COPY or DUMP or tracks PRINT, enqueues the VTOC during the entire operation
For a physical data set DUMP enqueues the VTOC during the entire DUMP

Restriction: The enqueue installation exit routine is not called during COMPRESS, CONVERTV, data set COPY, COPYDUMP, DEFRAG, CONSOLIDATE, logical data set DUMP, data set PRINT, or RELEASE processing.

You can use this exit to cause DFSMSdss to enqueue the VTOC only for the duration of the VTOC access. If you do not enqueue the VTOC for the entire operation, you can improve performance and decrease the chance of deadlock. However, there is a trade-off. With the improved performance and reduced chance of deadlock, there is also decreased data integrity.