Page 288 - ExtendSim User Guide
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Resources and Shifts
Resource requirements
Overriding the policy so utilization is maximized
If Maximize resource utilization is checked, the default resource allocation policy is overrid- den. In that case, resources can be allocated to a lower priority item regardless of the impact that might have on satisfying the requirement of a higher priority item.
☞ If Maximize resource allocation is checked, a lower priority item could “scavenge” any needed resources from those reserved for higher priority items. This could significantly impact when, or even if, higher priority items get their requirements met.
Overriding the resource requirement rank
As discussed in “Sorting criteria” on page 261, one of the properties that waiting items can be sorted by is the resource requirement rank. The resource requirement rank is a single value that applies by default to every resource that is part of the particular resource requirement. A resource requirement rank must be  0; the default resource requirement rank is 1.
On the Resource Manager’s Policies tab, the
resource requirement rank can be overridden
for an individual resource. This means that,
only for the specified resource, a resource
requirement’s rank will differ from the original
value entered on the Requirements tab. Since a
resource requirement could be composed of
multiple resources, each resource that is part of
a resource requirement can override the resource requirement’s rank with a different value.
Overriding is accomplished by changing the values in the RR Rank column in the table labelled Override resource requirement rankings.
☞ The original ranking values are displayed in square brackets in the RR Rank column.
Resource requirements
A resource requirement is a named rule that specifies how many of what types of resources to allocate to an item. An advanced resource queue will only release an item if the resources required by the item are available. Resource requirements are created:
• Manually,asdiscussedbelow
• By default, as discussed starting on page 268
Hierarchy of a resource requirement
Resource requirements are developed in the Requirements tab of the Resource Manager block. They are created using a three-level hierarchy of components:
1) Resourcerequirementsarethetoplevelcomponent.Theyconsistofquantityexpressions.
2) Quantityexpressionsarecomponentsthatarecreatedatthemiddlelevelofthehierarchy. They consist of filtering conditions.
3) Filteringconditionsarecreatedatthebottomlevelofthehierarchy.
Steps to take before creating
Before creating a resource requirement, it is helpful to perform the following steps: 1) Identifythecomponentsthatwillbeneeded:
a)Determine how many distinct collections of resources are required
Wash/Wax resource requirement is ranked higher
Discrete Event

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