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.