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 usually 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 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 a variety of protocols. Support for a protocol may be 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 in conjunction 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 utilizes
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 utilize 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
utilize this interface.