Disk space allocation is controlled through SUBPOOL records in the DASD CONFIG file. SUBPOOL records associate certain allocation parameters with a name that is referenced during allocation. Subpools do not directly define the space to be allocated, but contain DASD extent definitions that the subpool can use.
The actual disk storage definition begins with a VOLUME record that specifies the disk’s volume label and its device type. Each contiguous block of disk space on a volume that is to be allocated for user minidisks must be defined with an EXTENT record that follows the corresponding VOLUME record. Exact definitions indicate the beginning and ending cylinder or block address and the names of the subpools from which allocations can be made. The extents cannot overlap. You can also specify extents to be used by CP.
At system startup, CA VM:Director uses the records in the DASD CONFIG file to construct a disk storage layout. Each user definition is examined, and a complete storage map, defined at the minidisk level, is created in virtual memory. No minidisk, except those specifically listed in the DASD CONFIG file to be ignored, is allowed to overlap an extent definition or another minidisk.
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