Backup control data set

The backup control data set (BCDS) provides DFSMShsm with information defining the backup and dump environment. DFSMShsm needs this information to manage its backup data sets and volumes. DFSMShsm updates the contents of the BCDS with current backup version information.

Backup Control Data Set (BCDS)

Required:

No, not for space management and general DFSMShsm processing. DFSMShsm requires a BCDS if you want to use the incremental backup, dump, ABARS, or fast replication functions.

Allocated by starter set:

Yes, see Starter set example.

Maximum record size:

6544 bytes, if you need 100 or less active backup versions of any data set, if you use dump class stacking values greater than 99, or if you use fast replication.
2093 bytes, if you need 29 or less active backup versions of any data set, or if you use dump class stacking values of 99 or less.
2040 bytes, if you need 29 or less active backup versions of any data set, or if you use dump class stacking values of 97 or less.

Note:

The total number of backup versions for a data set may exceed the maximum number of active backup versions when a RETAINDAYS value is specified. Additional records are created to contain the retained backup versions. For more information about specifying a RETAINDAYS value, see the BACKDS command in z/OS DFSMShsm Storage Administration.
Any time the BCDS maximum record size is changed, the BCDS must be reorganized.

Data set type:

VSAM key-sequenced data set (KSDS).

Storage guidance:

See Considerations for DFSMShsm control data sets and the journal.

The control data sets are backed up at the beginning of automatic backup and are backed up differently from user data sets. The way control data sets are backed up depends on how you specify the SETSYS CDSVERSIONBACKUP command. For more information about specifying the CDS backup environment, see Defining the backup environment for control data sets.

For information about the control data sets in a multiple DFSMShsm-host environment, see CDS considerations in a multiple DFSMShsm host environment.