The processor control elements tables can add installation processors (PCEs) to a JES2 system or override JES2 processors.

The JES2 PCE tables represent units of JES2 work. The JES2 dispatcher gives control to a PCE. No other PCE gains control until, and unless, this PCE directly relinquishes control. This is done when JES2 issues a $WAIT. When a $WAIT is done, control passes to the JES2 dispatcher, which saves the registers in the PCE control block that represents the JES2 processor and then dispatches another JES2 processor. A JES2 processor is ineligible for dispatching until it is $POSTed.

PCEs can be generated during JES2 initialization or after initialization. Therefore, you can specify that a processor be created and be present for the life of JES2 or that it be created only upon installation demand (that is, after initialization).

You can also specify when the processor is given control. For example, you can specify if you want a processor to be given control concurrent with the HASPWARM processor for final initialization processing. Or, you can specify that the installation processor doesn't need to take control until initialization has completed but concurrent with the other JES2 processors. You can also indicate that a processor only gets control when it is $POSTed for work.

Processors can also be associated with a device by pointing to a particular DCT table from the PCE table. This is a one-to-one correspondence, that is, one PCE is associated with one device.