Examples of DPL

This section gives some examples to illustrate the lifetime of the mirror transaction and the information flowing between the client program and its mirror transaction.

Figure 28. DPL with the client transaction issuing a syncpoint
 The picture consists of three columns. The left column represents System A, the right System B, and the middle column what flows between the two systems.  An application on System A issues an EXEC CICS LINK PROGRAM('PGA') COMMAREA(...) request. An Attach mirror, 'LINK' request is sent to System B. System B attaches the mirror transaction, which performs the LINK to program PGA. PGA runs and issues a RETURN command. The mirror ships the commarea back to System A. System A passes B's reply to the application, which issues an EXEC CICS SYNCPOINT request. The SYNCPOINT request is sent to System B. On System B, the mirror takes the syncpoint, frees the session, and terminates. A positive response is sent to System A. On System A, the syncpoint is completed and the application continues.

Figure 28 shows a DPL request on which the client transaction issues a syncpoint. Because the mirror is always long-running, it does not terminate before SYNCPOINT is received.

Figure 29. DPL with the server program abending
 The picture consists of three columns. The left column represents System A, the right System B, and the middle column what flows between the two systems.  An application on System A issues an EXEC CICS LINK PROGRAM('PGA') COMMAREA(...) request. An Attach mirror, 'LINK' request is sent to System B. System B attaches the mirror transaction, which performs the LINK to program PGA. PGA runs but abends. An abend condition is sent to System A. The mirror waits for a syncpoint or an abend from the client region. On System A, the client program abends. On System B, the mirror terminates. An abend message is sent to System A. The session is freed. On System A, the abend message is routed to CSMT.

Figure 29 shows a DPL request on which the server program abends.

Related concepts
Overview of DPL
Intersystem queuing
Related tasks
Statically routing DPL requests
Dynamically routing DPL requests
Daisy-chaining of DPL requests
Defining local resources for DPL
Defining remote resources for DPL
Application programming for CICS DPL
Related reference
Limitations of DPL server programs
Appendix A. Intercommunication rules and restrictions checklist
[[ Contents Previous Page | Next Page Index ]]