View the number of connections to the Oracle database and the user __python

1, query the number of Oracle connections
Select COUNT (*) from v$session;
2, query Oracle's concurrent connection number
Select COUNT (*) from v$session where status= ' ACTIVE ';
3. View the number of connections for different users
Select Username,count (username) from V$session where username are not null GROUP by username;
4. View all Users:
SELECT * from All_users;
5, view the user or role system permissions (directly assigned to the user or role system permissions):
SELECT * from Dba_sys_privs;
SELECT * from User_sys_privs;
6. View the rights included in the role (see only the roles owned by the logged on user)
SELECT * from Role_sys_privs;
7, view the User object permissions:
SELECT * from Dba_tab_privs;
SELECT * from All_tab_privs;
SELECT * from User_tab_privs;
8. View all roles:
SELECT * from Dba_roles;
9. View the roles owned by the user or role:
SELECT * from Dba_role_privs;
SELECT * from User_role_privs;

10, to see which users have SYSDBA or Sysoper system permissions (the query requires appropriate permissions)
SELECT * from V$pwfile_users;