When is this a problem?
When you have an unnecessary top level on a list that does not need to be summarized. Examples include a transaction list, currency list, or any other list you are using for an indicator where you do not need to see a top level or summary.
Why is this a problem?
When you have an unnecessary top level on a list, the engine runs calculations and recalculations that can cause a decrease in performance. This happens when summary settings are left on. Any change in a value will cause a recalculation for the summary on the top level.
How to correct:
Remove the parent of all from the list.
More information:
Planual 1.05-05
Planual 1.05-06
Planual 1.05-07
Understanding Top Level
Top Level Item and Parent Hierarchy
Questions on this topic? See Does the list include a top level when it is not necessary? in our Model Optimization Checklist forum.