Ensuring that exit routines exist at the CALL
If the work involved in setting up information for the CALL request
is costly, you might issue the QUERY request with the QTYPE=CALL parameter
to find out whether any exit routines are associated with the exit.
This step would help you avoid the steps that lead up to a CALL request.
Here is an example, in pseudocode, of using the QUERY request:
Issue REQUEST=QUERY with TYPE=CALL
IF retcode indicates "there are exit routines" THEN
set up parameter list
Issue REQUEST=CALL
ELSE
do "no exit routine" default processing
ENDIF