How to Kill Session in SQL

First you need to identify which object is locked and then identify session id.

For identifying session run below query.

SELECT O.OBJECT_NAME,
       S.SID,
       S.SERIAL#,
       P.SPID,
       S.PROGRAM,
       SQ.SQL_FULLTEXT,
       S.LOGON_TIME
  FROM V$LOCKED_OBJECT L,
       DBA_OBJECTS O,
       V$SESSION S,
       V$PROCESS P,
       V$SQL SQ
 WHERE     L.OBJECT_ID = O.OBJECT_ID
       AND L.SESSION_ID = S.SID
       AND S.PADDR = P.ADDR
       AND S.SQL_ADDRESS = SQ.ADDRESS
       AND o.object_name = <object name>;

Use below statement to kill the session.

  ALTER SYSTEM KILL SESSION '<sid>,<serial#>'