Coding Rules

Specific coding rules for the entry environment and register usage and a list of return codes for each routine are provided on the following pages. Follow these general rules when coding a CA MIC exit routine:

Note that all CA MIC routines are invoked through the standard parameter list pointed to by Register 1. The common exit interface is described in the CA MIM Resource Sharing for z/VM Programming Guide.
Preserve all registers except 0, 1, and 15.
All CA MIM exit routines execute under GCS; therefore, you should use GCS macros when coding the routines. Also, you will need to assemble the routines using the GCS macro libraries.
Avoid using the GCS OPEN, CLOSE, LOAD, LINK, BLDL, or WTO macros, or any other GCS macro that implicitly or explicitly calls the WAIT supervisor.
Do not use the STIMER or TTIMER macros.
Provide a save area of at least 72 fullwords if you want to issue messages from the GCMCMDXT exit routine. If you do this, use the subroutine provided and do not change register 11.
Make sure that the GCMCMDXT routine uses the appropriate command authority levels in each situation. If you change the command authority level for a user through a LINK command, CA MIC uses the authority level assigned through the LINK command.
Use the SETOPTION EXIT command to identify the appropriate load module for your routine. If you use a module name other than the exit name, specify the load module name on the LOAD operand. For example, specify SETOPTION EXIT=GCMCMDXT LOAD=EXIT1 when you are using the load module named EXIT1 for the GCMCMDXT routine. See CA MIM Resource Sharing for z/VM Statement and Command Reference Guide for detailed information about this command.
To assemble an exit, you must use High Level Assembler.

Assemble and link-edit each completed routine as an authorized load module with the module name you specified on the SETOPTION command. Link-edit routines into the authorized load library for CA MIM, and include the load library on the GLOBAL LOADLIB command in the PROFILE GCS file for the MIMGR service machine. LINKEXIT EXEC, which is provided on the distribution tape, links exit routines into a load library named MIMEXITS LOADLIB.

For more information on the MIMCMDXT exit routine, see the CA MIM Resource Sharing for z/VM Programming Guide.