Before starting a calculation, Essbase searches the database outline and marks complex formulas that require top-down calculation; for example, a member formula that contains a cross-dimensional reference. When Essbase reaches a member with a top-down formula, it does a top-down calculation for the member.
When a formula on a member is complex, all possible blocks for the member must be examined to see if an existing block must be changed or a new block created; it is difficult to determine the dependency that blocks have on other blocks before the start of the calculation. The top-down method slows calculation performance because Essbase must search for appropriate blocks to calculate to execute the formula.
When a formula is compiled, if the formula is to be calculated top-down, Essbase logs a message in the application log file.
Consider the following complex formula:
A = B -> D + C -> D
To calculate the formula, Essbase must examine every combination of A to see whether B -> D or C -> D exists.