Chapter 6 Working with PDMs
OLAP cubes are usually filled with data from a data warehouse database.
As mentioned in section Understanding object mapping, it is possible to skip the data warehouse step and have an OLAP engine directly filled from an operational database. However this is not very common, and supposes fairly small amounts of data to manipulate. In this section, we will consider the case of OLAP database filled with data from a data warehouse.
You can link PDM objects to create a relational to multidimensional mapping between physical objects and OLAP objects. With this link, it will be possible to generate text files containing data warehouse data. These text files can be used to populate OLAP cubes.
The following table lists object mapping in a relational to multidimensional mapping:
| Data warehouse object | OLAP object |
|---|---|
| Table (Fact type or children tables) | Fact |
| Table (Dimension type or parent tables) | Dimension |
| Column | Attribute of a fact or measure of a dimension |
The relational to multidimensional mapping implies:
For more information on creating a data source, see section Creating a data source in a PDM.
Operational and data warehouse data are designed in physical diagrams and OLAP data are designed in multidimensional diagrams.
Automatic mapping
When you use the Rebuild Cubes feature to create cubes and dimensions from fact and dimension tables, the mapping between source tables and OLAP objects is automatically performed. For more information on the Rebuild Cubes feature, see section Rebuilding Cubes in chapter Building Multidimensional Diagrams.
The relational to multidimensional mapping is used to generate cube data in text files to be loaded by OLAP engines.
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