Optimizing Resource Selection in the Scheduler

To improve the performance of the Scheduler's processing of a resource request queue, you can try using the following resource selection rules:

• First Load
• First N Loads
• Minimum Setup First Load
• Minimum Setup First N Loads
• Threshold

These rules are faster because they consider only a portion of the possible load requests in the Scheduler's request queue.

Be aware that using these rules can result in unexpected behavior.

For example, situations can occur where the resource becomes free, sorts the request queue using the selection rule, fails to make an allocation, goes idle, and remains idle. In this situation, the resource remains idle until one of the following occurs:

• A load processes an operation where it needs the resource.
• The resource goes off-shift and then back on-shift.

The resource remains idle for the rest of the Scheduler run because another load never needs the resource and the resource is not on a shift. This leads to a related issue. Each time you use the selection rules First Load and First n Loads, load requests at the top of the request queue may "block" load requests further down in the queue. For example, this will occur if:

• First Load is the selection rule for resource RES1.
• The first load in the RES1 request queue requires resources RES1 and RES2.
• RES1 is free, but RES2 is not.

Resource RES1 will remain idle until the system can either allocate RES2 to the waiting load, or another load processes an operation where it needs RES1, or RES1 goes off shift and then back on shift.