List DB Sessions and Kill

Query to list DB Sessions:

Login as sys  user.

SELECT s.inst_id,
       s.sid,
       s.serial#,
       p.spid,
       s.username,
       s.program
FROM   gv$session s
       JOIN gv$process p ON p.addr = s.paddr AND p.inst_id = s.inst_id
WHERE  s.type != 'BACKGROUND';

Kill DB Session:

SQL>ALTER SYSTEM KILL SESSION 'sid,serial#';