Intercommunication methods

CICS® can communicate with other systems that are in the same operating system or sysplex using multiregion operation (MRO). To communicate with other CICS or non-CICS systems that are not in the same z/OS® image or sysplex, CICS connects using either a TCP/IP (IPIC) or SNA (ISC over SNA) protocol.

Communication between systems

For communication between CICS and non-CICS systems, or between CICS systems that are not in the same operating system or z/OS sysplex, you usually require a network access method to provide the necessary communication protocols.

CICS TS supports two such intercommunication facilities:
  1. Transmission Control Protocol/Internet Protocol (TCP/IP)
  2. ACF/SNA, which implements the IBM® Systems Network Architecture (SNA)

Communication between systems over TCP/IP is known as IP interconnectivity (IPIC). The generic name for communication between systems over SNA is intersystem communication (ISC) or intersystem communication (ISC) over SNA.

IPIC and ISC are used to connect CICS and non-CICS systems or CICS systems that are not in the same z/OS image or sysplex. These intercommunication facilities can also be used between CICS regions in the same z/OS image or sysplex. For example, you might create an ISC connection between two CICS regions in the same sysplex if you require two connections between them and there was already an MRO connection.

Multiregion operation

For CICS-to-CICS communication, CICS provides an interregion communication facility that does not require the use of a network access method such as ACF/SNA or TCP/IP. This form of communication is called multiregion operation (MRO). MRO can be used between CICS regions that reside in the same z/OS image or in the same z/OS systems complex (sysplex).

Note: The external CICS interface (EXCI) uses a specialized form of MRO link to support communication between z/OS batch programs and CICS.