JES2 uses workload management classification services to assign a service class to each job after it is converted, regardless of its job class. The service class is assigned based on WLM rules which can include attributes such as Job Class, Job Name, Job Priority, Userid, Job Accounting Information, and PERFORM= specification on the JOB statement. See z/OS MVS Planning: Workload Management for details.

You should take care not to classify both JES2 managed classes and WLM managed classes into the same service class. Workload management may not be able to effectively meet its goals if some jobs are initiated through JES2 and others through the WLM.