The global trap/trace exit

The global trap/trace exit (DFHTRAP) is intended to be used only under the guidance of IBM® Service personnel. It is designed so that a detailed diagnosis of a problem can be made without having to stop and then restart CICS®.

Typically, the global trap/trace exit is used to detect errors that cannot be diagnosed by other methods. These might cause intermittent problems that are difficult to reproduce, the error perhaps occurring some time before the effects are noticed. For example, a field might be changed to a bad value, or some structure in storage might be overlaid at a specific offset.

DFHTRAP is an assembler language program that can be invoked whenever the trace (TR) domain is called to make a trace entry. The trap must be activated before it is used, either dynamically or at CICS initialization.

A skeleton version of DFHTRAP is supplied in both source and load-module forms. The source of DFHTRAP is cataloged in the CICS640.SDFHMAC library. The source of the skeleton DFHTRAP contains comments explaining its use of registers and DSECTs, and the coding you need to do if you need to use the exit.

The code in DFHTRAP must not make use of any CICS services, cause the current task to lose control, or change the status of the CICS system.

Related Concepts
Information passed to the exit
Actions the exit can take
Program check handling

Related Tasks
Establishing the exit
Coding the exit
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