The DFSMSdss Cross Memory Application Interface is based on a client/server model. IBM® products that make use of the DFSMSdss Cross Memory Application Interface include IMS™ Image Copy (IC2) and DFSMShsm. DFSMSdss also provides a JCL interface for this support.

            //S1 EXEC PGM=ADRXMAIA,PARM='TYPRUN=NORUN'
                            in place of
            //S1 EXEC PGM=ADRDSSU,PARM='TYPRUN=NORUN'

The DFSMSdss Cross Memory Application Interface support provides the capability for client applications to connect to and interact with a separate DFSMSdss server address space using a user-provided Interaction Module (UIM). DFSMSdss processing that is performed on behalf of a connected client application is controlled by one or more jobstep tasks that are executing in the server address space. The DFSMSdss server address space may be created by issuing a START command or may result from the ASCRE macro that is issued by the Cross Memory Application Interface support that is invoked by the client application.

After a DFSMSdss server address space begins execution, module ADRXMAIB is given control by the system, and directs server processing. The server processing that is performed on behalf of a client is referred to as a work thread, and it executes under a unique jobstep task. The jobstep task invokes the ADRDSSU program for each work thread request that the client application makes. A server can concurrently process multiple client work threads for multiple client-connected address spaces. Each work thread is a separate instance of an ADRDSSU jobstep task. Multiple server address spaces may exist and be concurrently processing on behalf of multiple client address spaces.

A client application invokes module ADRXMAIA to utilize the DFSMSdss Cross Memory Application Interface support. When a client application invokes ADRXMAIA, DFSMSdss attempts a connection to the client-identified server address space. If the client-identified DFSMSdss server address space does not exist, the Cross Memory Application Interface invokes the ASCRE macro to create the server. If the client does not provide a server address space identifier, "DFSMSDSS" is used as the default server address space identifier. The JCL interface uses "DSSBATCH" as the default identifier unless the ASPACE parameter supplies it.

You can also create a DFSMSdss server address space using a START command that specifies an appropriately named member in SYS1.PROCLIB. The procedure must invoke module ADRXMAIB. The proclib member name should match the server identifier that is used by client applications or match batch jobs that use the JCL interface that will be connecting to the server that is created.

A DFSMSdss server address space that was created using the ASCRE macro goes into termination mode if there is no more work to do after all connected client applications terminate. There is a delay period prior to a server termination. Any connection request during this delay period causes the server to revert to processing mode to process the work threads that are associated with the connecting clients.

DFSMSdss server address spaces remain active as long as a client remains active unless the operator MODIFY command informs the server that it should stop processing after all current work threads are completed, for example F DFSMSDSS.DSSBATCH,STOP or F DSSBATCH,STOP.

A DFSMSdss server that is started with a START command does not enter termination mode when all work is completed. You must use the MODIFY command to stop it.