DFSMShsm-owned volumes contain low activity and inactive user data sets that were moved (migrated data) or copied (dumped and backed up data) into the DFSMShsm-owned portion of the storage hierarchy. The data is stored in a space-saving format. The data stored in a space-saving format is not directly accessible by users, but must be returned to a level 0 volume in user format before users can access it. Information about DFSMShsm-owned data is recorded in the inventory maintained in the DFSMShsm control data sets.

Migration level 1 and migration level 2 volumes

Low activity data is stored on migration level 1 (ML1) and migration level 2 (ML2) volumes. The DFSMShsm automatic management of ML1 and ML2 volumes can be supplemented by DFSMShsm commands to manage them manually.

Backup tapes

Backup tapes contain the backup copies of data sets placed there on a daily basis.

Spill backup tapes

Spill backup tapes contain data moved from backup volumes as a result of recycle processing. The data is written in a DFSMShsm space saving format. The recycle function is a tape consolidation process performed on ML2 and backup tapes that become sparsely populated with valid data.

Dump tapes

Dump tapes contain all the data of a physical volume and are written in a DFSMSdss space saving format. Several dumps from different DASD volumes can be automatically stacked onto a single tape.

Aggregate data tapes

Aggregate data tapes contain user defined groups of data sets that were copied by aggregate backup for recovery at a remote site. Aggregate control tapes can contain control information, data from level 0 DASD, data from ML2 and user tape, and instruction and log data.

Alternate tapes

ML2 and backup tapes can have alternate tapes. The alternate tapes are produced by either duplicating the original tapes, or by using the duplex tape function to concurrently create a copy when the original ML2 or backup tapes are created. Alternate tapes provide site disaster protection, supplementing the ABARS (aggregate backup and recovery support) aggregates and protecting against media damage.

Fast replication target volumes

Fast replication target volumes contain the fast replication backup copies created during DFSMShsm fast replication processing. Fast replication target volumes are defined within copy pool backup storage groups.