Through the DSPSERV macro, supervisor state and PSW key 0 - 7 programs can create a data space that consists of disabled reference (DREF) storage. DREF storage is storage that can be referenced by callers that are running disabled. DREF storage uses more system resources than non-DREF storage because the system does not page DREF storage out to auxiliary storage. Instead, it uses central storage (and expanded storage, if your processor has it). IBM® recommends that you not use DREF storage when pageable storage is sufficient.

To request DREF storage, code DREF=YES on the DSPSERV CREATE macro. A data space with DREF storage can be SCOPE=SINGLE, SCOPE=ALL, or SCOPE=COMMON.