QUEUE

The QUEUE module is used to model a waiting space before a SELECT or hold type module (ACCESS, ALLOCATE, COMBINE, GROUP, PREEMPT, PROCEED, REQUEST, SCAN, SEIZE or WAIT). The QUEUE module may have a finite capacity and entities which arrive after the limit has been reached are sent to the balk label.

Blockages are used to 'block' upstream processes controlling entity arrival at the queue.

Prompt	Valid Entry	Default
Queue ID	Queue number or name	-
Capacity	Expression truncated to an integer	Infinite
Balk label	Module label to which the balked entity is to be sent	Dispose the entity
Blockage level	Expression truncated to an integer	None
Blockage	ID Blockage number or name	None

Examples

Prompt	Value
Queue ID	2
Capacity	15
Balk label	rejectjobs

When the capacity of queue number 2 exceeds 15 entities any further arriving entities are sent to the module with label 'rejectjobs'

Prompt	Value
Queue ID	partbuffer
Blockage level	NQ(partbuffer)+NE(process) > 4
Blockage ID	Noroom

A queue named 'partbuffer' sets blockage 'Noroom' when the number in the queue (NQ) plus the number of entities en route (NE) exceeds 4. The blockage would be defined upstream with the 'BLOCK' module. The en route values can only be evaluated if a 'STATION' module preceeds the queue module