APPC/IMS overview

APPC/IMS, a part of IMS TM, lets you use the CPI Communications interface to build CPI application programs.

APPC/IMS allows distributed and cooperative processing between IMS and systems that have implemented APPC as shown in the following figure. APPC/IMS delivers support for APPC with facilities provided with APPC/MVS. (The APPC/IMS interface is provided by APPC/MVS and supports the CPI Communications interface. IMS TM supports the CPI resource recovery interface.) APPC/IMS supports the CPI resource recovery Commit (SRRCMIT) and Backout (SRRBACK) calls for IMS-managed local resources. These protected resources include:
  • IMS TM message-queue messages
  • IMS DB databases
  • Db2 for z/OS® databases

APPC/IMS also supports the existing IMS DL/I application programming interface (API) enabling application programs to use LU 6.2 communications without the function of the CPI Communications interface. This allows most existing applications to continue to function with the APPC/IMS support of LU 6.2.

Figure 1. APPC support for IMS
An application running in IMS (which is running on z/OS) communicates with an application running on, in this example, UNIX.
Definitions:
  • Within the context of administering IMS TM, transaction programs, applications, application programs, and programs are synonymous.
  • Within the context of administering APPC/IMS and LU 6.2 devices, APPC application programs are synonymous with LU 6.2 application programs.
  • LU 6.2 transactions are those that originate from an LU 6.2 application program.
Recommendations: For APPC/IMS, do the following:
  • Schedule your IMS standard or modified application programs entered from LU 6.2 remote systems using MSC. Be aware that CPI-C driven application programs cannot have transactions that execute on remote systems.
  • Define your APPC/IMS LUs for use by APPC/MVS, as well as by any APPC application program.
  • Use the LTERM and the MOD name in the first segment of your message. Use the LTERM to change the destination for your output to a non-LU 6.2 device. Use the MOD name to format error messages.
  • Use a network-qualified LU name. You do not need to have unique names for the LUs on different systems.

IMS dependent regions are automatically defined to APPC as subordinate address spaces of the IMS Scheduler. An IMS BMP cannot be defined as an ASCH controlled application. It may use explicit conversation services through the IMS base LU.

IMS manages the APPC/IMS message buffers automatically; no definition is necessary. No special considerations are needed for EMH.