System performance can suffer if too many jobs and/or sessions are running
at the same time. Setting limits on the number of jobs and sessions that can
run concurrently protects the system from inadvertent or deliberate attempts
to degrade its performance. Setting limits on the number of active devices in
use at any time helps control the user load, and also helps prevent access by
unauthorized users.
Additional methods for controlling resources and security are provided
by the Access Control Definition Facility.