Aggregations Redundancy Oracle Tips by Burleson Consulting

The Data Warehouse Development Life Cycle

Aggregating Data For The Oracle Warehouse
Note: For more information on using triggers and snapshots to update your Oracle data warehouse, see Chapter 9, Distributed Oracle Data Warehouses.

Once the extraction and loading details have been determined, we need to take a look at the levels of summarization for our aggregate tables. Several methods can be used to aggregate data within OLAP servers. As you can see in Figure 6.1, the ROLAP method extracts data from the relational engine, summarizing the data for display. The other popular method manually pre-aggregates the data and keeps the summarized data ready for retrieval. This chapter focuses on those techniques.

Figure 6.1 Aggregation and OLAP servers.

It is important to remember that aggregation is a form of data redundancy, because the aggregations are computed from other warehouse values. As such, we must always keep in mind that some pre-calculated averages may need to be recomputed as new data is loaded into our warehouse.

This is an excerpt from "High Performance Data Warehousing".

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