Lets say someone asked you what are the Oracle database built-in accounts (Oracle internal) in your current database ?
Most oracle database dictionary views have a column called ORACLE_MAINTAINED that was introduced in Oracle 12c release.
SQL> select username,last_login,oracle_maintained from dba_users where oracle_maintained=’Y’;
Finding Oracle built-in roles:
SQL> select role,oracle_maintained from dba_roles where oracle_maintained=’Y’;