Kill locked SQL Sessions

Step1: 

SELECT c.owner,

  c.object_name,

  c.object_type,

  b.sid,

  b.serial#,

  b.status,

  b.osuser,

  b.machine

FROM v$locked_object a ,

  v$session b,

  dba_objects c

WHERE b.sid     = a.session_id

AND a.object_id = c.object_id;

Step2: Kill the respective session by executing following alter command

ALTER SYSTEM KILL SESSION 'SID,SERIAL#';