Most data warehouse practitioners create aggregated data tables to dramatically improve the performance of highly summarized queries. These aggregate tables store precomputed results that are aggregated measures (typically summed) over a set of dimensional attributes. Using aggregate tables is a typical technique used to improve query response times in decision support systems.
If you write SQL queries or use a tool that only understands what physical tables exist and not their meaning, then using aggregate tables becomes more complex as the number of aggregate tables increases. The aggregate navigation capability of the Oracle BI Server allows queries to use the information stored in aggregate tables automatically. The Oracle BI Server lets you concentrate on asking the right business question, and then the server decides which tables provide the fastest answers.
Oracle Business Intelligence has an aggregate navigation feature to take advantage of those aggregates in source databases, for more information, see Managing Logical Table Sources (Mappings). However, it can be time consuming to create and maintain the data aggregation, as well as load database scripts and the corresponding metadata mappings. For that reason, Oracle Business Intelligence provides an aggregate persistence feature that automates the creation and loading of the aggregate tables and their corresponding Oracle Business Intelligence metadata mappings.
This chapter contains the following topics: