Summary
This chapter described the creation and use of aggregates and multi-cubes. Aggregates, a key technique for improving query performance, can be used in multi-cube queries. Without resorting to aggregates, a complex query on a large multi-cube may experience an unacceptable response time.
Key Terms
| Term | Description |
|---|---|
| Aggregate | An aggregate is a subset of an InfoCube. The objective when using aggregates is to reduce I/O volume. The BW OLAP processor selects an appropriate aggregate during a query run or a navigation step. If no appropriate aggregate exists, the processor will retrieve data from the original InfoCube. |
| Multi-cube | A multi-cube is a union of basic cubes. The multi-cube itself does not contain any data; rather, the data reside in the basic cubes. To a user, the multi-cube resembles a basic cube. When creating a query, the user can select characteristics and key figures from different basic cubes. |
For Further Information
• OSS Note 0175534, "Large BW Systems and Performance of Aggregate Build."
• OSS Note 0379736, "How Does a MultiCube Work?"
• OSS Note 0327876, "MultiCube Query and Using Several Aggregates."
Next…
Chapter 9 discusses the Operational Data Store (ODS).