Before and After Aggregation

Question

Hi Gurus'
Where can we find the options "Before Aggregation" and "After Aggregation"?What is the basic use of these aggregations?Why we should not use the option called Before Aggregation in a  Multiprovider?
Could any one please let me know the above..
Thanks!
James

Answer 1

Hi James,
Aggregation
This function is only available for formulas and calculated key figures.
You can make settings for aggregation and calculation time (for the detail level of the calculated key figure or formula) here. By default, the data is first aggregated to the display level; the formula is then calculated (= standard aggregation). The exception aggregation setting allows the formula to be calculated before aggregation using a reference characteristic, and to be then aggregated with the exception aggregation.
You can select the following settings in the Exception Aggregation field.
●      Use Standard Aggregation: You use this setting to specify that aggregation is to take place before calculating the formula. Therefore, you do not use exception aggregation.
●      Sum
●      Maximum
●      Minimum
●      Exception If More Than One Record Occurs
●      Exception If More Than One Value Occurs
&#9679;      Exception If More Than One Value <> 0 Occurs
&#9679;      Average of All Values
&#9679;      Average of All Values <> 0
&#9679;      Average Weighted with Calendar Days
&#9679;      Average Weighted with Working Days
You can specify the ID of the factory calendar in Customizing. For more information see the SAP Reference IMG  ® SAP Customizing Implementation Guide ® SAP NetWeaver ® Business Intelligence ® Settings for Reporting and Analysis ® General Settings for Reporting and Analysis Set F4 Help and Hierarchies for Time Characteristics/OLAP Settings.
&#9679;      Counter for All Detailed Values
&#9679;      Counter for All Detailed Values That Are Not Zero, Null, or Error
&#9679;      First Value
&#9679;      Last Value
&#9679;      Standard Deviation
&#9679;      Variance
If you use exception aggregation, you must select a characteristic from the Reference Characteristic field, using which the system can calculate the formula before aggregation. In the Reference Characteristic field, you can select from all characteristics that are available in the InfoProvider.
For more information about the setting for exception aggregation, see the documentation for InfoObject maintenance under Tab Page: Aggregation.
Calculate After Aggregation: This field is only displayed for calculated key figures; it is not displayed for formulas. It is used for display and stipulates that the formula of the calculated key figure is calculated after aggregation. If you use calculated key figures that you defined in SAP BW 3.5, you can use this field to specify whether the formula is to be calculated before or after aggregation.
Calculating before aggregation results in poor performance because the database reads the data at the most detailed level and the formula is calculated for every record. In formula calculations, often the single record information for just one or two specific characteristics is required; the remaining data from the InfoProvider can be aggregated.
We recommend that you control the calculation level using an exception aggregation with the corresponding reference characteristic. If you require multiple exception aggregations or reference characteristics, you can nest formulas and calculated key figures in one another and specify an exception aggregation for each formula or calculated key figure.
For more information,
Examples of Exception Aggregation Last Value (LAS) and Average (AV0)
Tab Page: Aggregation
Hope it Helps
Srini