Invoking the assembler user exit

For debugging purposes, the CEEBXITA assembler user exit can be invoked during:

Enclave initialization
Enclave termination
Process termination

The functions of the CEEBXITA user exit depend on when the user exit is invoked and whether it is application-specific or installation-wide. Application-specific user exits must be linked with the application load module and run only when that application runs. Installation-wide user exits must be linked with the Language Environment initialization/termination library routines and run with all Language Environment library routines. Because an application-specific user exit has priority over any installation-wide user exit, you can customize a user exit for a particular application without affecting the user exit for any other applications.

At enclave initialization, the CEEBXITA user exit runs prior to the enclave establishment. Thus you can modify the environment in which your application runs in the following ways:

Specify runtime options
Allocate data sets/files in the user exit
List abend codes to be passed to the operating system
Check the values of routine arguments

At enclave termination, the CEEBXITA user exit runs prior to the termination activity. Thus, you can request an abend and perform specified actions based on received return and reason codes. (This does not apply when Language Environment terminates with an abend.)

At process termination, the CEEBXITA user exit runs after the enclave termination activity completes. Thus you can request an abend and deallocate files.

The assembler user exit must have an entry point of CEEBXITA, must be reentrant, and must be capable of running in AMODE(ANY) and RMODE(ANY).

You can use the assembler user exit to establish enclave termination behavior for an enclave ending with an unhandled condition of severity 2 or greater in the following ways:

If you do not request an abend in the assembler user exit for the enclave termination call, Language Environment honors the setting of the ABTERMENC option to determine how to end the enclave.
If you request an abend in the assembler user exit for the enclave termination call, Language Environment issues an abend to end the enclave.

For more information on the assembler user exit, see z/OS Language Environment Programming Guide.