Queueing

By default, the capacity of a Queue block (the maximum number of entities that it is permitted to store in its buffer) is infinity. You can set the capacity of a Queue block by using the Capacity field in the Block Properties dialog box, or you can dynamically set the capacity by using the InCapacity port on the Queue block. Valid incoming values for the InCapacity port are integers greater than or equal to zero. If the capacity of a Queue block is reduced dynamically during the simulation run, any excess entities are removed from the block (according to the selected queueing policy) and sent out through the OutBalk port. If there are no connections to the OutBalk port, the entities are destroyed.

If you dynamically change the capacity of a Queue block by using the InCapacity port, then you need to reset the capacity to the initial starting value at the start of the next run. Otherwise, the next run of the model will use the final capacity from the previous run. When dynamically changing the Queue block capacity during a run, you can ensure that the capacity is set to the correct initial starting value for each run by defining a factor for the Queue block capacity. You can then specify the initial starting capacity in the Experiment window so that the initial Queue block capacity is set at the start of the run. For more information about defining factors and anchors, see Chapter 5: Experiments.