The use of private disks for the generations of an FGG precludes the simultaneous use of other volumes for the generations of this FGG.
The group entry and the file generation entries are written into the F1 label of the private disk. By means of the CATAL macro (operand DISP=REUSE) or CREATE-FILE-GROUP and MODIFY-FILE-GROUP-ATTRIBUTES commands (operand OVERFLOW-OPTION= REUSE-VOLUME) the user can specify, in the catalog entry, that the volume containing the oldest generation (which is to be deleted) is to be used for storing a new generation. If the old generation being deleted extends over several disks, the new generation is cataloged only on the first disk of the series.
The user must remember the following with regard to the above-mentioned operands: the space occupied by the generation to be deleted is released only after the new generation has been created. If the private disk is full when the user attempts to create a new generation by means of the FILE macro or CREATE-FILE-GENERATION command, DMS cannot carry out the primary allocation for this new generation and the macro or command will be rejected due to the lack of storage space.
In contrast to FGGs on pubsets, FGGs or generations on private disks can be exported (by means of the ERASE macro, operands CATALOG/DELETE-OR-EXPORT/VOLUME or the EXPORT-FILE command) and imported into the system again at any time.