If the data set does not exist on a level 0 volume, you can create it. If a backup version of the data set exists, you need not create the data set. DFSMShsm performs a recovery of the backup version (which creates the data set) then invokes DFSMSdss to restore the data set. If you are a DFSMShsm-authorized user, DFSMShsm still attempts to restore the data set even if it is not cataloged and no backup version can be found. The restored data set is not cataloged. In this case, you must use the Access Method Services DEFINE RECATALOG command to catalog the data set again. If a new name was specified, it is passed to DFSMSdss. If you are not a DFSMShsm-authorized user, the recovery fails and DFSMShsm issues an error message if the data set is not allocated and no backup version can be found.
If the data set is cataloged, DFSMShsm invokes DFSMSdss, specifying REPLACE, and passes the management class name and storage class name. DFSMSdss attempts to restore the data set over the top of the existing data set. If the space is too small, DFSMSdss fails the request, and DFSMShsm writes the DFSMSdss error message in the dump activity log and issues an error message to the user.
If you specify NEWNAME and the NEWNAME data set is cataloged when the original data set is not cataloged, DFSMShsm first recovers the backup version of the original data set, using the storage class and management class appropriate to the NEWNAME data set. DFSMShsm then restores the dump copy of the data set over the top of the recovered data set. Finally, DFSMShsm deletes the cataloged NEWNAME data set and renames the restored data set to the new name.