Each task in an address space has a limit priority and a dispatching priority associated with it. The control program sets these priorities when a job step is initiated. When you use the ATTACH or ATTACHX macro to create other tasks in the address space, you can use the LPMOD and DPMOD parameters to give them different limit and dispatching priorities.
The dispatching priorities of the tasks in an address space do not affect the order in which the control program selects jobs for execution because that order is selected on the basis of address space dispatching priority. Once the control program selects an address space for dispatching, it selects from within the address space the highest priority task awaiting execution. Thus, task priorities may affect processing within an address space. Note, however, that in a multiprocessing system, task priorities cannot guarantee the order in which the tasks will execute because more than one task may be executing simultaneously in the same address space on different processors. Page faults may alter the order in which the tasks execute.