Just like the storage space on public volumes, space on private disks is requested by means of the FILE macro or the CREATE-FILE and MODIFY-FILE-ATTRIBUTES commands. DMS makes the private disk available to the participating jobs for the duration of the requests.
Any amount of storage space can be requested on private disks, limited only by the capacity of the disk. The user may use relative space allocation with primary and secondary allocations for a private disk. Furthermore He/she can specify the disk on which space is to be allocated. The user can also use the absolute allocation to specify which PAM pages are to be reserved.
Extending storage space
Storage space is extended by means of the FILE macro or the MODIFY-FILE-ATTRIBUTES command. If the user does not specify VSNs in the VOLUME operand, the system attempts to reserve space on the last disk which contains the file. If there is not enough space on the disk to meet the entire request, space is reserved on other private disks recorded in the catalog.
If VSNs are specified in the VOLUME operand, the system attempts to reserve storage space on the specified volumes. If there is not enough space free, a partial allocation is made. Disks whose VSNs are recorded in the catalog but not specified in the current macro or command call are ignored.
If a file which, until now, has existed on one private disk is to be extended on a second private disk, the operands VOLUME, DEVICE and SPACE must be specified.
If a large amount of additional space is needed, it is better to request it in several small units, which will probably be assigned on different disks. If a file extends over several private disks, all of these disks must be mounted when the file is opened.
Releasing storage space
The user can release storage space that has been reserved or not allocated by means of the FILE macro (operand SPACE=<-n>) or via the operand SPACE=*RELEASE in the MODIFY-FILE-ATTRIBUTES command. If the catalog entry indicates DESTROY=YES, the space released in this manner is overwritten. In this case, the private disk must be accessible when the macro or command is issued to release the space.