All users on an Oracle database usually have the privilege to display a list of database users, without the additional security information. It is useful to be able to do this as you may want to contact someone belonging to the database or find out who is sharing the same tablespaces and privileges as you. Administrators will check this list frequently as they add and delete users from the database when new employees start or when projects come to an end.
Open up a command line session in Oracle SQLPlus to display the "SQL>" prompt. Commands can be entered from here, including the ability to list users in the database.
Type in "select * from all_users;" on the command line. This will display all users' basic details in the database.
Enter "select * from dba_users;" on the command line. This will display all users and the attributes for each user, including account permissions, tablespaces used and other pertinent information. The password cannot be retrieved from this view, as it is encrypted.