The two parts of a catalog, the BCS and the VVDS, require different backup techniques: the BCS can be backed up like other data sets, whereas the VVDS can only be backed up as part of a volume dump. The entries in the VVDS and VTOC are backed up when the data sets they describe are exported with access method services, logically dumped with DFSMSdss, or backed up with DFSMShsm.