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.
|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."
Chapter 9 discusses the Operational Data Store (ODS).
Part I. Guided Tours
Business Scenario and SAP BW
Creating an InfoCube
Loading Data into the InfoCube
Checking Data Quality
Creating Queries and Workbooks
Managing User Authorization
Part II. Advanced Topics
Aggregates and Multi-Cubes
Operational Data Store (ODS)
Generic R/3 Data Extraction
Appendix A. BW Implementation Methodology
Appendix B. SAP Basis Overview
Appendix C. Glossary
Appendix D. Bibliography