DISPATCH_QUEUE_PRIORITY_BACKGROUND
Tasks run at the background priority, which is equivalent to the background quality-of-service level.
Declaration
var DISPATCH_QUEUE_PRIORITY_BACKGROUND: Int32 { get }Discussion
Use quality-of-service constants instead. This constant maps to the QOS_CLASS_BACKGROUND class.
Items dispatched to the queue run at background priority; the queue is scheduled for execution after all high priority queues have been scheduled and the system runs items on a thread whose priority is set for background status. Such a thread has the lowest priority and any disk I/O is throttled to minimize the impact on the system.