The ODI Repository for Oracle BI Applications comprises two repositories: master and work.
Master Repository. Topology of resources, security, version management. A master repository is usually associated with multiple work repositories, but work repositories are always attached to a single Master repository
Work Repository. Contains data models and projects. This is the development and execution repository.
The master and work repositories must reside in the same database schema, and the database type must be Oracle. Both the master and work repositories are set up during the Oracle BI Applications installation process.
The default ODI repository ID is 500. This ID is part of the internal ID for every object that is created within the ODI repository. Having a repository ID greater than or equal to 500 is critical to ensure that the objects you create do not overlap with any current or future Oracle BI Applications objects. If you change the default ODI repository ID, make sure the new value is greater than 500.