Removing Table Lock

Login to database as SYS or SYSTEM user. Find out the SESSION_ID by running the following SELECT statement
SELECT SESSION_ID
FROM DBA_DML_LOCKS
WHERE NAME = Table Name;

Use this session id to find SERIAL# by using following SELECT statment
SELECT SID,SERIAL#
FROM V$SESSION
WHERE SID IN (SELECT SESSION_ID
FROM DBA_DML_LOCKS
WHERE NAME = Table Name)

Use ALTER SYSTEM command to KILL SESSION and this will release the lock.
ALTER SYSTEM KILL SESSION 'SID,SERIALl#';