查看所有用户：select * from all_users;

查看表空间：select tablespace_name from dba_tablespaces;

查看用户具有怎样的角色：select * from dba_role_privs where grantee=’用户名’；

查看某个角色包括哪些系统权限：select * from dba_sys_privs where grantee=’DBA’

查看oracle中所有的角色：select * from dba_roles;