Defining indirect links for transaction routing

In some older releases of CICS® (no longer supported), indirect links between CICS regions were required for transaction routing across intermediate regions. In a network consisting solely of currently-available CICS systems, indirect links are only required if you are using non-z/OS® Communications Server terminals. Optionally, you can define them for use with z/OS Communications Server terminals. Indirect links are never used for function shipping, distributed program link, asynchronous processing, or distributed transaction processing.

The following figure shows the concept of an indirect link.
Figure 1. Indirect links for transaction routing
The picture shows a chain of four CICS regions, connected by MRO or APPC links. There is a TOR (A), two intermediate regions (B and C), and a back-end AOR (D). On the TOR, A, a transaction is defined as owned by intermediate region B. On B, it is defined as owned by the next intermediate region in the chain, C. On C, it is defined as owned by the AOR, D. On AOR D, it is defined as a local transaction. On TOR A, a terminal or connection is defined as local. On all the other regions, it is defined as remote, owned by TOR A. There are direct links between A and B, B and C, and C and D. On AOR D, there is an indirect link to A, by way of C. On C, there is an indirect link to A, by way of B.

This figure illustrates a chain of systems (A, B, C, D) linked by MRO or APPC links (you cannot do transaction routing over LUTYPE6.1 links).

It is assumed that you want to establish a transaction-routing path between a terminal-owning region A and an application-owning region D. There is no direct link available between system A and system D, but a path is available via the intermediate systems B and C.

To enable transaction-routing requests to pass along the path, resource definitions for both the terminal (which may be an APPC connection) and the transaction must be available in all four systems. The terminal is a local resource in the terminal-owning system A, and a remote resource in systems B, C, and D. Similarly, the transaction is a local resource in the transaction-owning system D, and a remote resource in the systems A, B, and C.