External Call Interface (ECI)

The External Call Interface (ECI) enables a client application to call a CICS® program synchronously or asynchronously. It enables the design of new applications to be optimized for client/server operation, with the business logic on the server and the presentation logic on the client.

The external interfaces allow non-CICS applications to access and update CICS resources by calling CICS programs. When used in conjunction with CICS communication, the external interfaces enable non-CICS programs to access and update resources on any CICS server. This method of using the external interfaces supports such activities as the development of graphical user interface (GUI) front ends for CICS applications and it allows the integration of CICS servers and non-CICS servers.

The application can connect to several CICS servers at the same time and have several called CICS programs running concurrently. The CICS programs can transfer information using COMMAREAs or channels.

CICS programs that are invoked by an ECI request must follow the rules for distributed program link (DPL) requests. For information on DPL requests, refer to your CICS server documentation.