The virtual subarea list provides the basic input to the page service functions: PGFIX, PGFIXA, PGFREE, PGFREEA, PGLOAD, PGRLSE, and PGOUT.
The list contains one or more doubleword entries; each entry describes an area in virtual storage. The list must be non-pageable and located in the address space to be processed. The VSL is not required to be on a word boundary.
For a description of the VSL, see z/OS MVS Data Areas in the z/OS Internet library.