The system library list (QSYSLIBL) is used as the first part of the library list associated with a job.
The libraries in the system part of the library list of a job are searched before any other libraries in the library list of a job. The list can contain as many as 15 names. You cannot delete or rename a library specified as part of the system library list, because libraries in this library list are locked.
You can change the system library list (QSYSLIBL). If you change QSYSLIBL, the change takes place immediately for new jobs entering the system. The change does not affect running jobs, unless the application in the job accesses the system library list directly.