In Classic star schema, dimension and master data table are same. But in Extend star schema, dimension and master data table are different. (Master data resides outside the Infocube and dimension table, inside Infocubecube).
In Classic star schema we can analyze only 16 angles (perspectives) whereas in extended star schema we can analyze in 16*248 angles. Plus the performance is faster to that extent.
Below are some of the basic differences between the two.
Classic Star Schema SAP BW Star Schema
Cube InfoCube
Fact Table Key Figure or KPI
Dimension Attribute Characteristic, Attributes, Hierarchy Node
Dimension Table Dimension Table, Master Data Table, External Table, SID Table
- Standard Business Content
- Hierarchies
- MultiCube
- Remote Cube
Advantages of Classic Star Schema
Data access runs performantly due to the small number of joining operations.
There are only join operations between the fact tables and the involved dimension tables.
Disadvantages of Classic Star Schema
Redundant entries exist in the dimension tables
Historization of dimensions is not easy to model. The dimension changing may be done slowly.
No multi language capability
It is difficult to model some hierarchy’s dimension.
Query performance is also made worse, since aggregates and fact data are stored in the same table (fact table).
Advantages of the SAP BW Star Schema
Faster access to data than via long alpha-numeric keys. SAP BW use automatically generated INT4 keys for SID and Dimension ID
Can model in easy way: Historizing, multi-lingual, and shared dimensions. It is happen because of the excavation of master data from the dimension tables using the SID technique.
The query performance is improved here as aggregated key figures can be stored in their own fact tables.
No comments:
Post a Comment