How to Kill the session when there is a lock on the objects you are working in TOAD or Sqlplus
select * from V$SESSION
where OSUSER like 'c_sgoud' -- User name of the terminal ( may be your windows login name )
Alter system kill session '146,46619'
select sid, serial# from v$session where username = 'USER';
alter system kill session 'SID,SERIAL#';