This is possibly a problem that is related to the SYSADM authorization requirements.
These are documented in the CA Fast Unload, under SYSADM Authorization Considerations:
The simplest way to test this problem, is to create a PFU member in your hlq.CDBAPARM Parmlib library, with the following syntax:
This tells Fast Unload to use the SYSADM1 user ID defined in the SETUP parmlib member.
Doing it this way will create a global default for all CA Fast Unload jobs,
including RC/Migrator jobs that are unloading data using Fast Unload.