Controlling DFSMShsm control data set recoverability

The DFSMShsm journal data set records any activity that occurs to the DFSMShsm control data sets. By maintaining a journal, you ensure that damaged control data sets can be recovered by processing the journal against the latest backup copies of the control data sets.

If you specify . . .	Then . . .
SETSYS JOURNAL RECOVERY	DFSMShsm waits until the journal entry has been written into the journal before it updates the control data sets and continues processing.
SETSYS JOURNAL SPEED	DFSMShsm continues with its processing as soon as the journaling request has been added to the journaling queue. (Not recommended.)

For examples of data loss and recovery situations, refer to z/OS DFSMShsm Storage Administration.