About User Security
You can secure users accounts through strong passwords and by specifying special limits for the users.
Each Oracle database has a list of valid database users. To access a database, a user must run a database application, and connect to the database instance using a valid user name defined in the database.
When you create user accounts, you can specify limits to the user account. You can also set limits on the amount of various system resources available to each user as part of the security domain of that user. Oracle Database provides a set of database views that you can query to find information such as resource and session information.
This section also describes profiles. Profiles provide a way to configure the resources for the database user. A profile is collection of attributes that apply to a user. It enables a single point of reference for any of multiple users that share those exact attributes.
Oracle Database provides a set of predefined administrative, non-administrative, and sample schema accounts. The Oracle Database installation guides provide a listing of these accounts. To find the status of these accounts, query the USERNAME and ACCOUNT_STATUS columns of the DBA_USERS data dictionary view.