Intersystem communication - IBM - AS/400

CICS intersystem communication allows a CICS system to access data and to run programs and transactions on remote CICS systems.In addition, distributed applications can be developed using the standard CICS application programming interface(API). Function may be spread between local CICS systems, remote CICS systems, and non-CICS systems that use advanced program-to-program communication(APPC). Function may be distributed to workstation-based clients. Moving the presentation logic to the workstation allows the development of user-friendly front-end processes that can take advantage of the graphical environment available on the workstation.

The communication facilities offered by CICS/400 are:

  1. Function shipping
  2. Function shipping allows your local transaction to request data from a CICS resource located at another CICS system. CICS/400 automatically routes the request to the required system. You are not aware that the request is being satisfied by a remote system.

  3. Transaction routing
  4. Transaction routing allows a user at any workstation to run any transaction in a remote CICS system. The transaction runs on the remote system but appears to the user as if it is running locally.

  5. Distributed program link
  6. Distributed program link (DPL) allows a local program to link to and run a program on another CICS system. When the remote program ends, control is returned to the initiating program. Distributed program link can be used to access host data that cannot be accessed by function shipping, such as DL/I and DB2 databases.

  7. Distributed transaction processing
  8. Distributed transaction processing (DTP) allows you to have a synchronous conversation between a local program and a remote program. The programs use CICS API commands to allocate and control Advanced Program-to-Program Communication (APPC) conversations. All this is transparent to the end user.

  9. Asynchronous transaction processing
  10. Asynchronous transaction processing allows you to initiate a remote transaction. The real significance of asynchronous transaction processing is that it can be used to balance the workload. You can control when the remote transaction is started by including a time in the parameters of the command that starts the remote transaction. This facility is usually considered as a form of function shipping with the resource being a transaction.

  11. Server support for workstation-based clients
  12. CICS/400 can act as a server to workstation-based client applications, allowing CICS/400 applications to have front-end graphical user interfaces.

Function shipping, distributed program link, and distributed transaction processing, take advantage of fully protected conversations (sync-level 2), where these are available. In this case, syncpoint control extends to both local and remote CICS resources, which means that the communicating systems cooperate to ensure that all involved recoverable resources are either committed or rolled back at each syncpoint. In the event of system or conversation failure, syncpoint control, together with CICS/400 support, takes the necessary steps to protect resources at the next available opportunity.

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