In general, CICS is a single system with associated data resources and network terminals that form a single system environment. It can also communicate with other systems that share similar communication capabilities in multi-system environments. This communication is called CICS intercommunication.

CICS intercommunication refers to the communication between a local CICS system and a remote system, which may or may not be another CICS system. This feature is particularly useful for interacting with external or remote systems that could be web-based or Java-enabled.

Intercommunication Terminology -

Below are the basic terminologies used in CICS intercommunication -

Command	Description
Sysplex	Sysplex is a combination of multiple MVS operating systems that work as a single system by sharing resources and functions. A sysplex is a set of z/OS systems that communicate with each other through specific 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.

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