1 | A way to classify level of database users. Like sysadm usually has superuser privileges, roles are used to group users with different privileges. |
2 | Because a DBMS system has many levels of operations which set many levels(kinds) of operation privilages, |
3 | Role is another logical level of grouping to define/specify who will have what system privileges. |
4 | It makes system management easier and more flexible. |