Creating retained backup copies

DFSMShsm maintains backup copies as active backup copies and retained backup copies. Active copies are the backup copies that have not yet rolled off. Retained copies are the backup copies that have rolled off from the active copies, but have not yet reached their retention periods. DFSMShsm can maintain a maximum of 100 active copies. DFSMShsm can maintain more than enough retained copies for each data set to meet all expected requirements.

Roll-off processing occurs when the number of existing active copies exceeds the maximum number of active backup versions, as defined by the management class attribute Number of backup versions (data exists) for SMS-managed data sets, and the value of the SETSYS VERSIONS command, for non SMS-managed data sets. When a new backup version causes the maximum number of active copies to be exceeded, DFSMShsm checks all of the active copies to see if any active copy has retained days specified, and if the retained days value is met. The active backup copies are then rolled off in the following order:

1. Roll-off processing removes all backup versions that have expired RETAINDAYS values.
2. If at least one active backup copy has retain days specified, but none of the active backup copies have met their retain days:
   1. The oldest active backup copy is rolled-off if it does not have a RETAINDAYS value specified.
   2. If the oldest active backup copy has RETAINDAYS value specified, then the oldest copy is replaced by the new backup copy, and the replaced active copy is maintained as a retained backup copy.
3. If none of the active backup copies have RETAINDAYS values specified, the excess versions are deleted, starting with the oldest version. The maximum number of active backup copies is 100.

When an active backup copy is rolled off from the active copies, but has not yet reached its retention period, DFSMShsm maintains it as a retained backup copy. DFSMShsm can maintain more than enough retained copies for each data set to meet all expected requirements. Generation and version numbers are not associated with retained copies and cannot be used to recover them. You can recover retained copies only by specifying the date, and optionally time, that the version was created.