Benefits of Shadow Calculations
The obvious question when dealing with Shadow Calculations is "why not just use custom calculations"?
Shadow Calculations offer the unique benefit of being the only kind of calculation in accoPLANNING that can facilitate writeback!
The result of a calculation will be saved in the SQL table for use in other data models or other use.
The result of the shadow calculation can be configured to be saved as the delta value between the prior result and the new result. This gives you a way to track if the result of a calculation has been changed including who and when it was changed.
Performance can be significant improved especially if you have leaf calculation requirements. This is especially important when you have multiply- or divide-calculations in combination with a hierarchy. Normal DAX calculation will multiply or divide the sum of two measures on a parent level and this will give an incorrect result. The sum of the leaf level result on a parent level will be the correct result. You need to make a complex SUMX calculation for it to work using DAX and it will perform badly. Shadow calculation will help improve performance and give you the correct result on the parent level as well.