Each job's library list consists of up to four parts: a system part, a user part, and the current and product libraries.
Only the system part will always be included in the library list.
When the system is shipped, the system value QSYSLIBL contains the names of the libraries to become the system part of the library list. The shipped values are QSYS, QSYS2, QHLPSYS, and QUSRSYS. The system value QUSRLIBL contains the names of the libraries to become the user part of the library list.
QSYSLIBL can contain 15 library names, and QUSRLIBL can contain 25 library names. To change the system portion of a job's library list, use the Change System Library List (CHGSYSLIBL) command. To change the value of either QSYSLIBL or QUSRLIBL, use the Change System Value (CHGSYSVAL) command. A change to these system values takes effect on new jobs that are started after the system values are changed.