There is an optional overhead associated with switching from one transaction to another. Context Switching Overhead is a resource attribute that specifies the amount of service time wasted when a server switches from one transaction to another.
Except during processor sharing, the elapsed time wasted is the Context Switching Overhead divided by the Service Rate Multiplier. During processor sharing, the Context Switching Overhead is assessed to each transaction at the beginning of its service. The elapsed time for the Context Switching Overhead to occur during processor sharing when T transactions are sharing S servers is:
The Context Switching Overhead is also applied to each transaction when it begins service after being preempted. If a server begins processing a transaction but is preempted before the context switching overhead has completed, the remaining service time of the transaction remains unchanged.