In a JES2 shared spool environment, you must initialize CA 7 with the CAS9 CAIRIM procedure on every LPAR in the JESPLEX even if no CA 7 submitted jobs will run on that LPAR. If no CA 7 jobs run on that LPAR you don't have to start ICOM, but the CAS9 CAIRIM initialization of the CA 7 environment must be done. When CA 7 submits a job, an indicator is put in the first job card so that when the job goes through the converter interpreter and the IEFUJV exit it is recognized as CA 7 submitted and an indicator put in the SMF common area. This is so that when subsequent SMF records are cut for the job (job start, step end, job end, etc.) our exits will be able to collect this data and feed it back to CA 7 via ICOM. In a JESPLEX, JES decides where the job goes through the converter interpreter. Usually a job is converted on the LPAR where it is submitted, but during heavy processing JES may pass this process to another LPAR. To be sure that this is what happened, you can check the JESLOG for a job that did not track and look for an IBM message:
IEFC025I INSTALLATION MODIFIED JCL
Checking a job that did track, you will see this message. The presence of this message means that when the job converted, the CA 7 environment was present on that LPAR. The absence of this message means it was not.