Interfaces to CICS transactions and programs

This book describes the following sources of external requests, and the routes that they can use into CICS®:

MQSeries® users
MQSeries users can use the 3270 CICS bridge to access CICS transactions. See Bridging to 3270 transactions
MVS™ applications
Applications running in MVS address spaces can use the External CICS Interface (EXCI) to access CICS programs. See External CICS Interface.
ONC RPC clients
ONC RPC clients can use CICS ONC RPC support to access CICS programs. See CICS ONC RPC support
DCE RPC clients
DCE RPC clients use the Application Support (AS) server to access CICS programs. See Using CICS as a DCE server.

The following types of external requests are described in other books:

User socket applications
User socket applications can use the CICS Sockets feature of CICS TS. See TCP/IP for MVS Version 3.1 CICS TCP/IP Socket Interface Guide and Reference.
Web browsers
Web browsers can use a variety of methods:
CICS Web support
The CICS Web support is a CICS-provided facility for supporting Web browsers. See the CICS TS for z/OS® Internet Guide
IBM® WebSphere®
The IBM WebSphere Application Server for OS/390® is an MVS application that supports Web browsers and routes their requests into CICS.
CICS Transaction Gateway
The CICS Transaction Gateway is a workstation application that can accept requests from Web browsers and route them into CICS. It uses the EXCI and ECI.
JVM applications
Java™ Virtual Machine applications can use a local gateway connection that uses the EXCI to pass requests to CICS. See Java Applications in CICS.
Java-enabled Web browsers
Java-enabled Web browsers can use applets that communicate with CICS. Writers of applets can use CICS-provided Java classes to construct external call interface (ECI) and external presentation interface (EPI) requests. The Web browsers communicate with Web servers, and with the CICS Transaction Gateway.
CICS client applications
CICS client applications use a distributed CICS client (either CICS Transaction Gateway or the CICS Universal Client ) and the ECI or the EPI. See the CICS Transaction Gateway: Programming Guide.
CICS programs
Programs running in CICS Servers on any platform can use EXEC CICS LINK to call a CICS program, or can use transaction routing to send transaction requests to CICS TS. Programs running in CICS TS can use the CICS front end programming interface (FEPI) to start transactions in the same or another instance of CICS TS. See CICS Front End Programming Interface User’s Guide.
Telnet clients
Telnet clients can use TN3270 to start transactions.
3270 users
Users of the IBM 3270 Display System can start transactions. This is the most familiar method of introducing work to CICS TS.

Figure 2 shows the principal ways of using CICS transaction processing services from outside CICS.

Figure 1. Key for External Interface diagram
 This is a key to the following diagram, showing the different shading used to identify CICS and other components and interfaces.
Figure 2. Client access to existing business logic
 This diagram shows the sources of external requests and the routes that they can use into CICS, as described in the preceding list.

Related concepts
The Client/Server concept
Distributed computing
TCP/IP protocols
ONC and DCE concepts
EXCI concepts
3270 bridge concepts
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