When you specify UNASSIGN with the DUMP parameter, UNASSIGN specifies that the volume is to remain known to DFSMShsm but must be removed from its current use. The volume is also disassociated from the dump class to which it is currently assigned. All records of the volume’s contents must be discarded. DFSMShsm can reuse the volume without reinitialization. If the volume is available for reuse, it is available to any dump class requiring a volume of the same unit type.