Journal data set size

The amount of space that you allocate for your journal data set depends on how often DFSMShsm automatically backs up the control data sets and the amount of DFSMShsm activity between backups. The journal data set requires sufficient storage to accumulate journal entries that occur between one control data set backup and the next. The automatic backup of the control data sets clears the contents of the journal.

Allocate the journal as a single volume, single extent data set that is contiguous and non-striped.

If you decide to change the size of a previously allocated and used journal, make sure that the newly allocated journal does not contain the EOF of the previous journal. You can do this in one of three ways:

Rename the old journal, allocate the new journal, and then delete the old journal.
Use IEBGENER (not IEFBR14) to allocate the new journal.
Allocate your new journal on a different DASD volume.