Access to a database server will be granted to a user based on the following types of user ID enrollment:
With open enrollment, every user has access to the SYSTEM user profile, giving every user potential access to the database server. You can create unique profiles for some users and allow other users to use the SYSTEM default profile.
With restricted enrollment, every user must have a unique user profile in order to access the database server. When setting up restricted enrollment, you delete the SYSTEM profile, which prevents users without unique profiles from accessing the database server.