Queueing

The Queueing Policy option in the Block Properties dialog box is used to define the order in which entities are stored in a Queue block. There are three queueing policies available in the Queue block: FIFO (first-in, first-out; the default), LIFO (last-in, first-out), and priority. When an entity arrives at a Queue block that is using a FIFO or LIFO queueing policy, the entity is stored at the appropriate end of the buffer. For Queue blocks that use a priority policy, the block extracts the priority value from an attribute defined for the entity and uses that value to determine where to place the entity in the buffer. The priority queueing policy also enables you to select an appropriate tie-breaking policy: FIFO, LIFO, or random.

In addition to setting the queueing policy by using the Block Properties dialog box, you can define a factor that is anchored to the QueueingPolicy anchor candidate for the Queue block and then set the queueing policy by using the Experiment window. For more information about the format of the Queue block QueueingPolicy factor candidate, see the section Queue Block. For more information about defining factors and anchors, see Chapter 5: Experiments.