ALTERDS command: Changing the back-ups for a non-SMS-managed data set

The DFSMShsm ALTERDS command alters the number of backup versions maintained for a non-SMS-managed data set and the frequency of creating the backup versions for the data set.

If an ALTERDS command is issued for an SMS-managed data set, the command fails and a message is issued. The number of versions and frequency of backup for an SMS-managed data set is determined from the data set’s management class attributes.

You can either specify new values with the VERSIONS and FREQUENCY parameters or revert to the DFSMShsm default values with the SYSVERSIONS or SYSFREQUENCY parameters.

When you specify a frequency of backup for your data set, the value overrides any frequency value you specified with the BACKVOL command or the current DFSMShsm value for FREQUENCY.
When you specify a value for the VERSIONS parameter for your data set, the value overrides the current DFSMShsm value for VERSIONS.
When you specify SYSVERSIONS or SYSFREQUENCY, DFSMShsm uses the value you specified with the VERSIONS parameter or the FREQUENCY parameter of the SETSYS command.

If you did not use the SETSYS command to specify these values, DFSMShsm uses the current DFSMShsm default values for the number of backup versions or the frequency of creation of the backup versions.

You do not have to repeat any of these parameters each time you start DFSMShsm because the values are stored in the BCDS data set record. The record is not deleted even if all of the backup versions for the data set are deleted. To delete this record from the BCDS, along with the record of each backup version, use the ALTERDS command with the SYSVERSIONS and SYSFREQUENCY parameters (reverts to DFSMShsm default values). Then use the BDELETE command to delete the backup versions.

If you specify the ALTERDS command without any parameters, you receive a message that the command has completed successfully. DFSMShsm, however, does not change any of the data set parameters that affect backup.