When a command contains system symbols, MVS™ provides the command text to command installation
exits
after it substitutes text for the system symbols. For
example, if the following command is entered to display a console
group on system SYS1:
DISPLAY CNGRP,G=(C1GP&SYSNAME.)
The command installation exit receives the following text:
DISPLAY CNGRP,G=(C1GPSYS1)
If a command installation exit requires the original command text
(the one that existed before symbolic substitution), the exit
can access the CMDXOLIB field in the command installation exit routine
parameter list (CMDX).
Note: Do not use command installation exits to add or change system
symbols in command text. The system cannot substitute text for system
symbols that are added or changed through those exits.
See the topic on
sharing system commands in z/OS MVS System Commands for
more information about using system symbols in commands.