CICS Transaction Gateway
IBM software that lets applications outside CICS, such as Java programs, call CICS programs over the network.
Also written CTG, ECI, external call interface
The CICS Transaction Gateway, or CTG, connects applications outside CICS to programs inside it. A Java application on a web server, for example, can call a CICS COBOL program, pass it data and get a result, as if it were calling a local service.
The main interface is ECI, the external call interface. The calling application names the CICS program and passes a COMMAREA or a channel, and the program runs in a CICS region in the normal way. To the CICS program, the request looks much like a LINK from another program.
CTG can run on z/OS, close to CICS, or on other platforms. It has been a standard way to connect web and Java applications to CICS for many years.
Today, sites have several options for the same job, including z/OS Connect for REST APIs and CICS's own web support. You will find CTG in many existing systems, so it is worth recognising the name and knowing that, behind it, there is usually an ordinary CICS program.
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- CICSThe transaction manager that runs online mainframe applications, and the software behind a great many screens bank staff use.
- EXEC CICSThe way a program asks CICS to do something, such as read a record, send a screen or call another program.
- COMMAREAThe communication area: a block of data a CICS program passes to another program, or keeps for the next step of a conversation.
- z/OS ConnectIBM software that makes mainframe programs and data available as REST APIs, so web and mobile applications can use them.
- MROMultiregion operation: the way CICS regions connect so that work started in one region can use programs and files in another.