In general, CICS is a single system with associated data resources and network terminals which is a single system environment. CICS can communicate with other systems that have similar communication facilities which is a multiple-system environment.

The communication used in multiple-system environment is called CICS intercommunication. CICS intercommunication is communication between a local CICS system and a remote system which might or might not be another CICS system. CICS intercommunication very useful to communicate with the external or remote system which might be web based or Java enabled.

Intercommunication Terminology -

Below are the basic terminologies used in CICS intercommunication -

Terminology Description
Sysplex Sysplex is combination of multiple MVS operating systems which works as a single system by sharing resources and functions.
A sysplex is a set of z/OS systems that communicate with each other through certain hardware components and software services.
A sysplex allows resource sharing between communicating systems.
CICSPlex CICSPlex is a combination of multiple interconnected CICS regions.
A CICSPlex is an environment in which multiple, interconnected CICS regions operate.
In CICSPlex, CICS and associated applications use the full capabilities of Parallel Sysplex architecture.
Local System A system which initiates the request for intercommunication.
Local Resource Resource which lies or used by the local system.
Remote System A system that receives the request from other system or local system.
Remote Resource Resource which lies or used by the remote system.

Intercommunication Facilities -

CICS supports below two intercommunication facilities -

  1. Transmission Control Protocol/Internet Protocol (TCP/IP)
  2. ACF/SNA, which implements the IBM Systems Network Architecture (SNA)

Intercommunication Methods -

CICS supports below two intercommunication methods -

  • Multi-Region Operation (MRO) - CICS can communicate with other systems that are in the same operating system or sysplex using multi-region operation (MRO).
  • TCP/IP or SNA protocol - To communicate with other CICS or non-CICS systems that are not in the same operating system or sysplex, CICS connects using either a TCP/IP (IPIC) or SNA (ISC over SNA) protocol.
    • IP InterConnectivity(IPIC) - Communication between systems over TCP/IP is known as IP interconnectivity(IPIC).
    • InterSystem Communication (ISC) - The generic name for communication between systems over SNA is intersystem communication (ISC) or intersystem communication (ISC) over SNA.