Overview of transaction routing

CICS® transaction routing allows terminals connected to one CICS system to run with transactions in another connected CICS system. You can distribute terminals and transactions around your CICS systems and still have the ability to run any transaction with any terminal.

Figure 1 shows a terminal connected to one CICS system running with a user transaction in another CICS system. Communication between the terminal and the user transaction is handled by a CICS-supplied transaction called the relay transaction.

Figure 1. The elements of transaction routing
The picture shows a TOR connected to an AOR by an IPIC, MRO or APPC link. A terminal is connected to the TOR, in which the CICS relay transaction is running. In the AOR, the user transaction is running.

The CICS system that owns the terminal is called the terminal-owning region or TOR, and the CICS system that owns the transaction is called the application-owning region or AOR. These terms are not meant to imply that one system owns all the terminals and the other system all the transactions, although this is a possible configuration.

The terminal-owning region and the application-owning region must be connected by IPIC, MRO, or APPC links. Transaction routing over LUTYPE6.1 links is not supported.

In transaction routing, the term terminal is used in a general sense to mean such things as an IBM® 3270, or a single-session APPC device, an APPC session to another CICS system, and so on. All terminal and session types supported by CICS are eligible for transaction routing, except those given in the following list:
  • LUTYPE6.1 connections and sessions
  • MRO connections and sessions
  • EXCI connections and sessions
  • IBM 7770 or 2260 terminals
  • Pooled 3600 or 3650 pipeline logical units
  • MVS™ system consoles

The user transaction can use the terminal control, BMS, or batch data interchange facilities of CICS to communicate with the terminal, as appropriate for the terminal or session type. Mapping and data interchange functions are performed in the application-owning region. BMS paging operations are performed in the terminal-owning region.

Pseudo-conversational transactions are supported, except when the “terminal” is an APPC session, and the various transactions that make up a pseudo-conversational transaction can be in different systems.