The fully qualified three-part name of the prestart job never changes once a prestart job is started. The user name of the fully qualified three-part job name always contains the user profile under which the prestart job is started.
If a spool file is opened before a prestart job handles any work request, the spool file is associated with the prestart job entry user profile. Otherwise, it is associated with the current user profile of the job.
If the prestart job entry profile and the current user profile are different, spooled files are spooled under a job with the job name being QPRTJOB and the user name of the current user profile. (This is also true for prestart job entries for server jobs.)
The class (CLS) parameter on the prestart job entry provides a way to control the performance characteristics of two classes of prestart jobs per prestart job entry.