To determine where you should go, you must first understand where you are.
This maxim defines the entire philosophy behind this phase of the database-design process. You must devote some time to gaining a clear understanding of your organization's database for these reasons:
To determine whether the database supports the organization's current information requirements
To uncover existing structural deficiencies
To determine how the database needs to evolve so that it will support the organization's future information requirements
You can use the existing database as a resource for developing a new database. However, you must carefully judge which aspects of the current database remain useful and ...