Upgrading IPIC

This topic tells you how to upgrade IPIC connections between CICS® systems when you migrate from one release of CICS to another. This information applies to all currently supported CICS TS releases, regardless of your current release and the target release.

If you are upgrading from an end-of-service release, you might need to take additional actions that are relevant to your current, end-of-service release, along with the actions summarized in the upgrade instructions provided below. For details, see Upgrading from end-of-service releases.

Upgrade actions

Your current version Action Mandatory or optional?
All versions Review selection behavior for IPCONN and CONNECTION resources across releases of CICS Mandatory

All versions Review selection behavior for IPCONN and CONNECTION resources across releases of CICS

If both an APPC or MRO connection and an IPIC connection exist between two CICS regions, and both have the same name, the IPIC connection takes precedence. However, if your terminal-owning region (TOR) and application-owning region (AOR) are in CICS systems that are using different levels of CICS, the rules can differ.

An APPC or MRO connection is defined with the CONNECTION resource. An IPIC connection is defined with the IPCONN resource.

If both CONNECTION resources and IPCONN resources are active in a CICS region, CICS searches for an IPIC connection first, so that when resources with the same name exist, the preference for an IPCONN resource can be maintained. However, if an IPCONN resource is not available, CICS attempts to route over an APPC or MRO connection by using a CONNECTION resource. If the request fails, a SYSID error is returned to the application that scheduled the request. For more information about how IPIC overrides default connections, see Changes to resources.

Table 1 and Table 2 show how the resources are used depending on the level of CICS installed at the communicating regions, the availability of resources, and the intercommunication method that is being used.
Table 1. Selection behavior for IPCONN and CONNECTION resources with TOR and AOR communications
Version of CICS in TOR or routing region Status of IPCONN resource CICS TS 5.1 to 6.1 AOR
DPL Asynchronous processing and transaction routing Enhanced Routing
CICS TS 5.1 to 6.1 Acquired IPIC connection IPIC connection IPIC connection
Released APPC or MRO connection APPC or MRO connection APPC or MRO connection
Table 2. Selection behavior for IPCONN and CONNECTION resources with AOR and ROR communications
Version of CICS in the AOR Status of IPCONN resource CICS TS 5.1 to 6.1 ROR
File control Transient data Temporary storage DL/I
CICS TS 5.1 to 6.1 Acquired IPIC connection IPIC connection IPIC connection APPC or MRO connection
Released APPC or MRO connection APPC or MRO connection APPC or MRO connection APPC or MRO connection