The default scheduling is a first-in-first-out policy. In other words, the first job that is submitted is the first job the scheduler examines in order to dispatch it to a queue. If the first job in the list of pending jobs finds a queue that is suitable and available, that job is started first. A job ranked behind the first job can be started first only if the first job fails to find a suitable free resource.
The default strategy is to select queue instances on the least-loaded host, provided that the queues deliver suitable service for the job's resource requirements. If several suitable queues share the same load, the queue to be selected is unpredictable.