An i5/OS™ thread competes with threads throughout the system for scheduling resources in addition to competing with other threads in the same job.
The system schedules processing resources by using a delay cost scheduler that is based on several delay cost curves (priority ranges).
On i5/OS, numerically lower priority values indicate higher priority with regard to scheduling. Adding its thread priority adjustment value to the job's priority specifies the priority of a thread. The default priority for a thread is no change from the process priority or a thread priority adjustment value of zero.
You can directly affect the application performance by assigning different thread priority adjustment values to the threads in your application.