The Physical layer of the Oracle BI repository contains objects that represent physical data constructs from back-end data sources.
The Physical layer defines the objects and relationships available to the Oracle BI Server for writing physical queries. This layer encapsulates data source dependencies to enable portability and federation.
Each data source of the repository model typically has its own discrete physical model in the Physical layer. The top-level object in the Physical layer is a database, and the type of database determines which features and rules apply to that physical model. For example, a relational database such as Oracle 12c has relational objects such as physical tables and joins. In contrast, a multidimensional source such as Essbase has cube tables and physical hierarchies. Therefore, some sections of this chapter apply to only certain database types.
Physical tables, cubes, joins, and other objects in the Physical layer are typically created automatically when you import metadata from the data sources. After these objects have been imported, you can perform tasks such as create additional join paths that are not in the data source, create alias tables for physical tables that need to serve in different roles, and adjust properties of physical hierarchies from multidimensional data sources.