Your iseries performance problems could be caused by seize/wait conflicts.

Have you ever had performance problems on your iSeries in which the CPU is barely being utilized but users are complaining that their jobs are running more slowly
than usual? You could be running into seize/wait conflicts. Seizes and locks can sometimes be a cause of significant wait times on your system. This document explains the difference between a seize and a lock and identifies how to determine whether seize/wait conflicts are occurring on your system