The 3270 bridge provides an interface so that you can run 3270-based CICS® transactions without a 3270 terminal. The 3270 terminal and end-user
are replaced by an application program, known as the client application. Commands for the 3270 terminal in the CICS 3270 user transaction are intercepted by CICS and replaced by a messaging mechanism
that provides a bridge between the client application and the CICS user transaction.
CICS provides two types of 3270 bridge mechanism:
- The Link3270 mechanism
- This mechanism is introduced in CICS Transaction Server for z/OS®, Version 2 Release 2 and provides a simplified interface
using LINK, ECI or EXCI. All messages have a fixed format and you are not
required to provide any user-written supporting programs. This mechanism supports
CICSPlex® load balancing; bridge facilities are shared between CICS regions on
the CICSPlex
- The START BREXIT mechanism
- This 3270 bridge mechanism requires a bridge
monitor transaction to initiate the bridge environment by issuing a START
BREXIT command, which specifies the target user transaction and also the name
of a user-written bridge exit. The bridge exit
is called to intercept 3270 requests and pass them in the form of messages
to the client application. You can write your own bridge exit and also define
your own message formats. Bridge exits are provided to support client applications
using Temporary Storage, the Web and MQSeries® as transport mechanisms for requests,
using sample message formats. This mechanism is single region only: bridge
facilities are local to the region.
The START BREXIT mechanism was introduced in earlier releases of CICS . It is still supported, and the sample bridge exits are still provided,
but you are recommended to use the simpler Link3270 mechanism, and migrate
to it where possible. The START BREXIT is not documented in this release of CICS . If you need to use it, or modify existing implementations, you should
refer to the CICS Transaction Server for OS/390®, Version 1 Release 3 External Interfaces Guide, which can be found in the CICS Transaction Server for OS/390, Version 1 Release 3 library
at:
http://www-4.ibm.com/software/ts/cics/library/books/os390/
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