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Mischa Spelt avatar image
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Mischa Spelt asked Matt Long answered

Resources: all or nothing

By default lists pull items as soon as the become available, unless you check All Or Nothing. I thought resources used lists but I ran into the following issue.

In the attached model I have a process to serve customers at one of two desks. Every hour the desks are closed for 5 minutes. I figured the simplest way would be to do something like the process on the left, where I just acquire the two resources and hold them for a while. However, as you see when running the model, the arrival of the customers always has at least one of the resources claimed so the Acquire for 2 never gets both of them.

I tried putting a Prority on the "Break" process to sort the back orders, but that doesn't work either. Now I can think of seveal solutions (change the resource to a list, or use a Zone, or acquire the operators one-by-one) but it feels like what is really missing here is a "FIFO" option that allows me to say "when it is time for coffee, either finish all customers in line or just the current one (depending on the back order queue strategy), then nobody gets a resource until the 'Acquire 2' has succeeded".

Any thoughts / comments?

PS FlexSim 17.0.1 still not in the dropdown :)

FlexSim 17.0.0
process flowacquire multiple resourcesbackorder queue strategy
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Sam Stubbs avatar image Sam Stubbs ♦ commented ·

Resources as to my knowledge are like lists, but in several ways are more simplified. Would you be able to initiate and use an actual list instead of resources to accomplish the logic?

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Matt Long avatar image
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Matt Long answered

The Resource is using a list behind the scenes (you can view the entries, back orders and list properties from the Resource properties tab), but as Sam stated, it is simplified. You don't get all of the same options as the List. Your model is prioritizing the back orders correctly, but the break token is waiting for two resources, not just one, so the Resource sees that 2 are not available and it skips over that back order.

Is there an issue with putting in two Acquire activities? One that acquires the first clerk and the 2nd that acquires the other?

This stops customers from acquiring the clerks. Then you just change the Release activity to Release All.


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