The system-wide data area QUSRSYS/QLILMTLIBL introduced in V5R1 that
controls library-lists was modified in V5R2. Did anyone else hear
about this? How did that slip past me?

(If you are like me and scared of modifying lots of CL for something
as important as liblists, possibly getting some RTVJOBA overruns,
then you will find this interesting.)

http://www-
919.ibm.com/servers/eserver/iseries/developer/os400/lib_list.html

In V5R2, the data area QUSRSYS/QLILMTLIBL is ignored. Some jobs can
run with a limit of 25 libraries while other jobs use a limit of 250
libraries. The limit for the user part of the library list is set to
25 if the data area QLMTUSRLIB is found in the job's library list,
the data area is TYPE(*CHAR), and the first character of the data
area is '1' (x'F1'). All other conditions result in a limit of 250.
The limit applies for the life of the job and is determined when a
job becomes active. The data area QGPL/QLMTUSRLIB ships with the
system and has a value of '0', so by default the support for long
library lists is enabled in V5R2.