Detail Explanation of Acceptance Test for Sporadic Jobs | Real Time System

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acceptance test for sporadic jobsAcceptance Test for Sporadic Jobs,
Real Time System Notes | Sixth Semester,
BSc.CSIT | Tribhuvan University (TU)

Acceptance Test for Sporadic Jobs
The minimum release times and maximum execution times of a sporadic job are unknown a priori. Consequently, it is impossible to guarantee a priori that all sporadic job can complete in time. A common way to deal with this situation is to have the scheduler perform an acceptance test when each sporadic job is released. During an acceptance test, the scheduler checks whether the newly released sporadic job can be feasibly scheduled with all the jobs in the system at the time.

If according to the existing schedule, there is sufficient amount of time in the frames before it’s deadline to complete the newly released sporadic job without causing any job in the system to complete too late, the scheduler accepts and schedules the job. Otherwise, rejects the new job. By rejecting a sporadic job immediately after the job is released, the scheduler gives the application system as much time as there is to take any necessary recovery action.

Example: Consider a sporadic job that activates a robotic arm, is released when a defective part is detected. The arm when activated removes the part from the conveyor belt. This job must be completed before the part moves beyond the reach of the arm. When the job cannot be scheduled to complete in time, it is better for system to have this information as soon as possible. The system can slow down the belt, stop the belt or alert an operator to manually remove the part.

Otherwise if the sporadic job were scheduled but completed late, its lateness would be detected until its deadline. By the time the system attempts a recovery action, the defective part may already have been packed for shipment, too late for simple recovery action to be effective.

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