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Client: Simulation error: Demand Generator active time overlap

This article applies to iGrafx Process and iGrafx Process for Six Sigma Client tools

You may receive the following types of errors when attempting to run simulation: 

 Error: <file>.igx - DefaultScenario:  Demand Generator 'Gen1_name' active time overlap with following generators that demand the same resource type.
Error: <file>.igx - DefaultScenario:  Demand Generator 'Gen2_name' active time overlap with Demand Generator 'Gen1_Name'.

You are receiving the errors from your Demand Generators because you are trying to trigger multiple Demand generators off of a single resource, and doing so is not allowed.  

Each Demand generator is designed to generate the number of transactions that will satisfy ALL of the available demanding resource units. So, for example, if you have two Demand generators demanding the same resource type and both are active (enabled during the same active time), when there resources become available at that period of time, the FIRST Demand generator listed will generate the full amount (the total number of available resource units) of transactions. That leaves no work for the second (and any additional) Demand generator(s) to do anything. The error message is thus informing you that the second (and so on) Demand generators are not going to be used, which is not what you specified, and is thus an error in modeling of the process. 

You may wish to investigate using the actual arrival of transactions into the process (e.g. with an interarrival or timetable generator), and let the transactions queue up if there are not resources available. If a single transaction triggers work in many different processes, you can use duplication of the transaction to start parallel work; either implicitly by having multiple output lines from a shape that is NOT a decision, or explicitly in the 'On Completion' tab of the Task page. You may also trigger parallel work using a 'broadcast' type message and the 'generate here' (by message) capability to cause a single transaction to spawn multiple requests all at once; assuming this is appropriate for your process. Again, it should be helpful to look at how the actual process works, and setup the generators to mimic that. 

iGrafx does offer consulting services to help you model your situation, should you need more in-depth help than our answer here provides. Please contact your iGrafx sales representative for more information. 

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