Passwords for database users are saved in the database's data dictionary. When a user tries to log into the database, his or her username and password are compared to the values in the database. If the username and password match, the user is granted database access. The data dictionary is kept in the database and may be accessed as long as the database is open. The dictionary also contains administrator passwords.  The data dictionary would be inaccessible until the database was locked. Because one of the administrator's responsibilities is to restart a down database, they must be able to log in even if the database is locked. That's where the password file comes in. A password file is an operating system file that is kept on a separate disc from the database. It saves the login and password for users with SYSDBA or SYSOPER access. When the database is unavailable, administrators with particular privileges are authenticated using password files.