Performance Optimization - Professional SQL Server Analysis Services 2005 with MDX - page 679

Figure 13-27
Analysis Services now applies all the aggregations designed for the Inter-
net_Sales_2001 partition to all the partitions selected. Once all the partitions
are applied with aggregation design, you need to process the partitions so
that Analysis Services creates the aggregated data. You can later send a
query that requests data for a specific level and analyze its performance. If
aggregations have been built for the cells that have been requested then
Analysis Services will serve the query from the aggregations. Based on the
size of your cube and aggregations designed you can notice performance
gain for queries touching the aggregations. Finally, you can use SQL Server
Profiler to see if specific aggregations are getting hit (you will see this later in
this chapter).
Usage-Based Aggregation Design
In addition to the Aggregation wizard, Analysis Services supports aggregation
design based on the user queries sent to Analysis Services. Designing ag-
gregations based on user queries is called usage-based optimization be-
cause aggregations are designed based on users' requests and making sure
performance gains are achieved for those specific queries. In order for Ana-
lysis Services to analyze the queries and design aggregations, the queries