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What does the dispatcher do? z/OS concepts |
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In z/OS®, the dispatcher component is responsible for routing control to the highest priority unit of work that is ready to execute. New work is selected, for example, when a task is interrupted or becomes non-dispatchable, or after an SRB completes or is suspended (that is, an SRB is delayed because a required resource is not available). The dispatcher processes work in the following order:
If there is no ready work in the system, z/OS assumes a state called an enabled wait until fresh work enters the system. Different models of the z/Series hardware can have from one to 54 central processors (CPs). Each and every CP can be executing instructions at the same time. Dispatching priorities determine when ready-to-execute address spaces get dispatched. An address space can be in any one of four queues:
Only IN-READY work can be selected for dispatching. |
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