This section covers migration for the 3270 bridge.
The existing 3270 bridge mechanism using the START BREXIT interface is still supported, and applications continue to run unchanged, but you are recommended to migrate to the new Link3270 mechanism.
The Link3270 mechanism is the recommended way to use the 3270 bridge. Use of the START BREXIT interface is not described in CICS® documentation for CICS TS Version 3, and you should refer to the publications for CICS Transaction Server for OS/390®, Version 1 Release 3 if you need to implement new applications using this interface.
In previous releases of CICS, the bridge mechanism required the client (end-user) application to send messages to a monitor program, which established the bridge environment by issuing a START BREXIT command. User-supplied (or sample) bridge exit and formatter user-replaceable programs translated 3270 commands to messages that were sent to the client.
A sample program, DFH0CBRM, is provided to assist migration to the Link3270 mechanism. To use it, change your monitor program to issue an EXEC CICS LINK to DFH0CBRM, instead of issuing a START BREXITcommand. DFH0CBRM converts existing messages to Link3270 format messages and drives the new Link3270 mechanism. Note that there are some changes to error processing, such as abend codes. Any restrictions in the use of the migration aid, which uses the MQSeries® CICS interface header (MQCIH), are described in comments in the source of DFH0CBRM, which is supplied in SDFHSAMP library. The generated version is supplied in SDFHLOAD, ready to use.
There is a one-to-one mapping between the old style message vectors and the Link3270 message vectors, but there are new fields in the Link3270 message header that should be reviewed if you want to exploit new function.
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