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qmgr -c 's sched default preempt_order = SCRD 50 R'
The scheduler will always assume jobs can be deleted. This means if D is connected to C or R, and a job is either -c n or -r n, the job will be considered for preemption. Deleting a job will return all resources used by the job back to the complex to be used by the high priority job. The pbs_deljob() IFL call will return normally returns back to the caller immediately after the server has received the request and started the delete process. Unlike pbs_deljob(), if jobs are to be deleted, the server will not return back to a pbs_preempt_jobs() call until all the jobs have been correctly fully preempted. This means if a job is to be deleted, the server will wait until the job is truly deleted before returning. This is because the scheduler needs the jobs to be out of the way before it starts the high priority job. If pbs_preempt_jobs() returned sooner, the scheduler would oversubscribe the nodes until jobs were finished being deleted.
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