An aggregate is a materialized, aggregated view of the data in an InfoCube. In an aggregate, the dataset of an InfoCube is saved redundantly and persistently in a consolidated form into the database.
Aggregates make it possible to access InfoCube data quickly in Reporting. Aggregates serve, in a similar way to database indexes, to improve performance.
We recommend that you create aggregates, especially in the following cases:
· The execution and navigation of query data leads to delays with a group of queries.
· You want to speed up the execution and navigation of a specific query.
· You often use attributes in queries.
· You want to speed up reporting with characteristic hierarchies by aggregating specific hierarchy levels.
An aggregate is made up of characteristics and navigation attributes belonging to an InfoCube. You can group the data according to different Aggregation Levels. In doing so, you can also store values for hierarchy levels belonging to an external hierarchy. Both time-dependent attributes and time-dependent hierarchies can be used in aggregates. Characteristics that are not used in the aggregate are brought together.
If you have created aggregates for an InfoCube and entered data for them, the OLAP processor automatically accesses these aggregates. When navigating, the different results are consistent. The aggregate is transparent for the end user.
New data is loaded at a defined time using logical data packages (requests) in an aggregate. After this transaction, the new data is available for rolling up in reporting.
“Performance Tuning for Queries with BW Aggregates” from the performance page for SAP Business Information Warehouse in SAP Service Market place
You can find additional information about MOLAP aggregates in MOLAP Store .