SLU P and ISC subsystems with DPM

If OPTIONS=DPAGE is specified, all fields within a logical page are transmitted together in one or more records. Additional logical pages are sent on request of the remote program or ISC subsystem for demand paging. This level of paging makes it more difficult for the remote program or ISC subsystem to process the data if more than one presentation page is included, but imposes less burden on IMS processing time.

If OPTIONS=MSG is specified, all the data within a message is sent together and no paging is performed. This technique might require more processing and logic in the remote program or ISC subsystem but is the best for IMS performance if all pages are actually used by the remote program or ISC subsystem. If many pages are not used by the remote program or ISC subsystem, this option results in unnecessary line traffic and IMS processing.

If autopage is specified (SCA byte 1, bit 5) and option PPAGE or DPAGE is desired for DPM-Bn, all data within the message is sent and no demand paging is performed.

The RCD statement can be used to influence the placement of fields within records. The DFLD that follows the RCD statement begins in the first user data location of a new record. Fields can be placed in records so that no field spans a record boundary, or so that logically related fields appear together in the same record.

Use of the RCD statement to set record boundaries can reduce transmission time and IMS processing time only if records of maximum length are created. If field placement into records is controlled using the RCDCTL specification only, the SPAN option causes the minimum number of records to be sent to the remote program. Use of SPAN requires, however, that the remote program put together the fields that have been split across records.