Before you create the physical layer of a repository, you need to plan, design, and then create a repository file.
The Physical layer of the Administration Tool defines the data sources to which the Oracle BI Server submits queries and the relationships between physical databases and other data sources that are used to process multiple data source queries. (Your licensing options determine whether you can add databases and connection pools to the physical layer.)
The first step in creating the physical layer is to create the schema. You can import the physical schema for supported data source types. You can import schemas or portions of schemas from existing data sources. Additionally, you can create the physical layer manually but it is a labor-intensive and error-prone activity