Users do not necessarily require individual accounts or schemas set up in each database. Alternatively, they can connect to a shared schema and be granted access to the objects associated with target applications. For example, suppose that users Tom, Dick, and Harriet require access to the Payroll application on the Finance database. They do not need to create unique objects in the database, and therefore do not need their own schemas, but they do need access to the objects in the Payroll schema.
Oracle Database supports mapping multiple users stored in an enterprise directory to a shared schema on an individual database. This separation of users from schemas reduces administration costs by reducing the number of user accounts on databases. It means that you do not need to create an account for each user (user schema) in addition to creating the user in the directory. Instead, you can create a user in the enterprise directory, and map that user to a shared schema. Other enterprise users can also be mapped to that schema.
For example, if Tom, Dick and Harriet all access both the Sales and the Finance databases, you do not need to create an account for each user on each database. Instead, you can create a single shared schema on each database, such as GUEST, that all three users can access. Then individual access to objects in the Sales or Finance database can be granted to these three users by using enterprise roles. A typical environment can have up to 5,000 enterprise users mapped to one shared schema and each user can be assigned a set of enterprise roles.
Oracle recommends that you create a separate shared schema that contains no objects to use as an entry point. Then, grant access to application objects in other schemas through enterprise roles. Otherwise, application objects can be inadvertently or maliciously deleted or altered.
In summary, shared schemas provide the following benefits:
Shared schemas eliminate the need to have a dedicated database schema on each database for each enterprise user.
Each enterprise user can be mapped to a shared schema on each database the user needs to access. The user connects to the shared schema when the user connects to a database.
Shared schemas lower the cost of managing users in an enterprise.