This activity includes:

• Identifying the persistent classes in the design
• Designing appropriate database structures to store the persistent classes
• Defining mechanisms and strategies for storing and retrieving persistent data in such a way that the performance criteria for the system are met

The database and persistent data storage and retrieval mechanisms, are implemented and tested as part of the overall implementation of the components and subsystems of the application.

The Designers responsible for persistent classes need to have an understanding of the persistence in general and the persistence mechanisms in specific. Their primary responsibility is to ensure that persistent classes are identified and that these classes utilize the persistence mechanisms in an appropriate manner. The Database Designer needs to understand the persistent classes in the design model and so must have a working understanding of object-oriented design and implementation techniques. The Database Designer also needs a strong background in database concurrency and distribution issues.

Persistence must be treated as an integral part of the design effort, and close collaboration between designers and database designers is essential. Typically the database designer is a 'floating' resource, shared between several teams as a consulting resource to address persistence issues. The database designer is also typically responsible for the persistence mechanisms; if the persistence mechanism is built rather than bought, there will typically be a team of people working on this. Larger projects will typically require a small team of database designers who will need to coordinate work between both design teams and amongst themselves to ensure that persistence is consistently implemented across the project.