In the realm of data warehousing, the star schema is a fundamental design pattern that facilitates efficient data retrieval and analysis. SAP Business Warehouse (SAP BW) employs a variant of this pattern known as the Extended Star Schema, which optimizes the way data is stored and accessed for reporting and analytics.
This article delves into the concept of the Extended Star Schema, its components, and why it plays a crucial role in SAP BW’s data modeling approach.
The Extended Star Schema in SAP BW is an evolution of the classic star schema used in data warehouses. Unlike a simple star schema, which consists of one central fact table connected to multiple dimension tables, the extended star schema introduces additional data structures and layers to improve flexibility, performance, and maintainability.
The extended star schema design addresses challenges faced in traditional star schemas such as:
SAP BW’s extended star schema organizes data so that detailed transaction data and master data attributes are separated but linked logically, improving query performance and data integrity.
In SAP BW, the fact table is primarily represented by the DataStore Object (DSO) or the Advanced DSO (aDSO). The DSO stores the detailed transactional data at the lowest granularity. It acts as the central repository for the fact data.
Dimension tables hold descriptive information or attributes related to facts, such as customers, products, time, and regions.
To support multilingual and descriptive texts, dimension tables are linked to separate text tables, ensuring flexibility in reporting.
InfoCubes in SAP BW serve as multidimensional cubes aggregating fact data along various dimensions for faster analytical queries.
| Aspect | Classic Star Schema | Extended Star Schema (SAP BW) |
|---|---|---|
| Fact Table | Single large fact table | Multiple DSOs or aDSOs as fact tables |
| Dimensions | Simple dimension tables | Master data with attributes & hierarchies |
| Aggregation | Fact table stores all aggregations | InfoCubes for aggregation and multidimensional analysis |
| Text Management | Text included in dimension tables | Separate text tables for multilingual support |
| Flexibility | Limited to fixed schema | Supports complex scenarios and hierarchies |
Imagine a sales reporting scenario:
This separation ensures detailed transactional reporting alongside fast summarized reports without duplication.
The Extended Star Schema is a cornerstone of SAP BW’s data warehousing strategy. By decoupling facts, master data, and aggregation layers, it delivers a flexible, scalable, and high-performance environment for enterprise reporting and analytics.
Understanding this design empowers SAP BW professionals to build efficient data models that meet complex business needs and deliver timely insights across the organization.