Below I provided the results of two following queries:
SELECT USERNAME, USER_ID FROM DBA_USERS ORDER BY USER_ID DESC;
SELECT ROLE, ROLE_ID FROM DBA_ROLES ORDER BY ROLE_ID DESC;
that display Oracle Database 18 users, roles and their IDs:
Oracle Database user and role IDs
statements, the operating system that operates Oracle can grant roles to users at connect time. Roles can be administered using the operating system and passed to Oracle Database when a user creates a session. As part of this mechanism, the default roles of a user and the roles granted to a user with the