Prioritization of Resources
In Model 14’s report page we found out, that the Project Manager has to wait for a Developer at activity Develop(internal) disproportionately long. This bases on the fact, that all the activities have the same resource priority assigned. The resource manager (internal feature of the simulation) allocates the process instances to the respective resource’s queue. Unfortunately the resource manager does not provide a sophisticated way to improve this allocation. It simply checks the activity’s resource priority, and then sorts the queue using this priority.
Furthermore, the resource manager inserts the lastly arrived process instance in the first place of the respective sorted sequence in the queue.
Example:
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One process instance of pool External Developers (PIED) has been started.
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It needs one Developer to work off the activity Develop (external)I
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Let’s assume, that there is no Developer available currently, so the PIED is being inserted into the Developer’s queue
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At the same time a process instance from the pool Software-Company (PISC) finishes the activity Plan Workload
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It now reaches the activity Develop (internal).
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Since it already has the Project Manager available it needs one of the Developers.
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Due to the fact, that all queues are using the first-in-first-out-principle and that all activities' resource priorities are the same, the PISC is being inserted behind the PIED into the Developer’s queue
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While that PISC waits for Developer, other PIEDs are being started (inter-arrival time of 1 hour) and inserted into the Developer’s queue
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Remember that all starting PISCs must wait at activity Plan Workload, because they wait for the single Project Manager, which is being held at activity Develop (internal)
This procedure is repeatedly executed. So, every following PISC has to wait longer for a Developer that the previous one. This is the result of equal prioritization of all activities in reference to the resources. All activities have the same importance for the queue and they are worked off using the FIFO (first in, first out) principle.
To avoid the behavior from the previous example, you can set the Resource Priority in the Simulation Properties of an activity (Optional Simulation Properties, see the figure below). This property defines the priority of an activity for the resource queue. There are five different levels (lowest, low, medium, high and highest). These levels are used to sort the activities in the queues of a resource pool, i.e. the higher the level, the more an activity is sorted to the fore.
