Summary of CICS intercommunication functions

As an introduction for new CICS® users, this section presents deliberately simplified definitions of the CICS intercommunication functions.

Function shipping

A program in system CICSA accesses resources (such as files or transient data queues) that are owned by remote system CICSB as though they were locally owned. The diagram shows a data-access request.

 The picture shows two CICS regions, CICSA and CICSB. A program on CICSA issues an EXEC CICS READ FILE request. Because the file is owned by CICSB, the request is shipped to CICSB. CICSB reads the file and returns the requested information to CICSA.

Asynchronous processing is an example of function shipping that does not access data - the shipped request is an EXEC CICS START command for a remote transaction.

Transaction routing

A terminal attached to system CICSA runs a transaction in remote system CICSB as though it were a local transaction.

 The picture shows two CICS regions, CICSA and CICSB. A terminal attached to CICSA starts a transaction. Because the transaction is owned by CICSB, CICSA passes the request to CICSB. On CICSB, the transaction runs. CICSB returns the response to CICSA.

Distributed program link

A program in system CICSA links a program in remote system CICSB as though it were running in the local system.

 The picture shows two CICS regions, CICSA and CICSB. A program on CICSA issues an EXEC CICS LINK PROGRAM request. Because the program is owned by CICSB, CICSA passes the request to CICSB. On CICSB, the program runs. CICSB returns the response to CICSA.

Distributed transaction programming

Two programs, one in system CICSA and one in system CICSB, communicate synchronously with each other. This dialog is called a conversation.

 The picture shows two CICS regions, CICSA and CICSB. Two programs, one on CICSA and one on CICSB, communicate synchronously with each other. Data flows back and forth between them.

Related concepts
Which intercommunication function?
Function shipping
Transaction routing
Distributed program link
Asynchronous processing
Distributed transaction programming
Related reference
CICS product communication support
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