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Merging several item flows into one stream
The Select Item In block can combine the inputs from any number of sources into one stream of output items.
☞ An alternative is to use the variable item input connectors on an Activity or other residence block.
Merging Inputs model
In the Merging Inputs example model, the Select Item In block will accept items from any of the three inputs. Its dialog is set to Select input based on: merge. If the Select Item In’s out- put is blocked, the block will force items to wait in the Queues (labeled Buffers 1-3). When the Select Item In becomes unblocked, it will check each input in turn to try to pull an item through for processing by the Activity. As you can see in the table that has been cloned from the Select Item In block, when it is ready to process items, the Activity gets whichever item is available. This can cause some queues to have longer waiting lines than others, as you can tell from their Results tabs.
Merging Inputs model
Balancing multiple input lines
To even out the queue lengths of multiple input lines, use a Select Item In block controlled by a Max & Min block (Value library), which checks the length of each queue. An example of this would be three loading docks that fill up as trucks unload, and you want items to come first from the dock that is most full.
Routing 159
Items from several sources
Discrete Event

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