CICS Transaction Gateway

The CICS® Transaction Gateway manages communication between servers and applications.

CICS Transaction Gateway

The CICS Transaction Gateway runs on a wide variety of operating systems. On the Windows, UNIX and Linux operating systems, it can access many different types of CICS server; on z/OS®, it can access only CICS Transaction Server for z/OS. On the Windows, UNIX and Linux operating systems, CICS Transaction Gateway uses a Client daemon to route External Call Interface (ECI), External Presentation Interface (EPI), and External Security Interface (ESI) requests to a CICS server. On z/OS, CICS Transaction Gateway can route only ECI requests, and has no Client daemon.

Communication between CICS Transaction Gateway and the Client application uses the following protocols:
  • TCP/IP sockets
  • Secure Sockets Layer (SSL)
TCP/IP sockets and SSL provide an efficient method of communication for intranet applications. CICS Transaction Gateway can manage many concurrent links to connected Web browsers. It can also control asynchronous conversations to multiple CICS servers. The multithreaded architecture of the CICS Transaction Gateway enables a single Gateway to support multiple concurrently connected users.
The CICS Transaction Gateway provides this functionality:
  • A Gateway daemon: The Gateway daemon communicates with CICS applications running on CICS servers through ECI, EPI, or ESI. For security reasons, it is typically resident on a Web server.
  • Gateway classes: This Java™ library includes classes that:
    • Provide application programming interfaces (APIs) for ECI, EPI, and ESI. This allows communication between Java Client applications and the Gateway daemon.
    • Allow Java Client applications to communicate with transactions on a server and handle 3270 data streams.
    • Allow your Java Client applications to use the SSL network security protocol.
  • J2EE resource adapters: These adapters provide a J2EE-compliant interface to CICS for your Java Client applications.
  • Client daemon: The Client daemon supports concurrent, ECI, and EPI calls to one or more CICS servers. The Client daemon can communicate with multiple CICS servers using various protocols. Support for a protocol canbe provided by one or more communication software products, so you can use the products best suited to your network environment. The way that the Client daemon operates, and the servers and protocols used for communication, are defined in the CICS Transaction Gateway initialization file. You can use the Configuration Tool to define these settings.
  • External access interfaces (ECI, EPI, ESI): An external interface allows non-CICS applications to access and update CICS resources by calling CICS programs, or by initiating CICS transactions. When used with the CICS communication facilities, it enables non-CICS programs to access and update resources on any CICS system. This supports such activities as developing graphical user interface (GUI) front ends for CICS applications, and allows the integration of CICS systems and non-CICS systems.
    • External Call Interface (ECI): The ECI enables a user 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.
      Note: The J2C Tools uses this interface.
    • External Presentation Interface (EPI): The EPI enables a user application to act as a logical 3270 terminal and so control a CICS 3270 application. It enables modern technologies, such as graphical or multimedia interfaces, to be used with traditional CICS 3270 applications.
      Note: The J2C Tools do not use this interface.
    • External Security Interface (ESI): The ESI enables user applications to verify and change passwords for specified user IDs that are managed by an external security manager (ESM) on a CICS server.
      Note: The J2C Tools do not use this interface.
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