The data dictionary views, also known as catalog views, let you monitor the state of the database in real time:
The views prefixed with
DBA_, show information about schema objects that are owned by you (
USER_), accessible by you (
ALL_) or accessible by a user with SYSDBA privilege (
DBA_). For example, the view
ALL_TABLES shows all tables that you have privileges on.
V$ views show performance-related information.
_PRIVS views show privilege information for different combinations of users, roles, and objects.