Terminate inactive database sessions from oracle database

Terminate all inactive sessions ..which are inactive for more than 3 hours & then kill the
    processes from O/S
   
    Run the below sql's and spool the out put
   
    select 'alter system kill session '||''''||a.sid|| ','||a.serial#||''''||';'
      from v$session a, v$process b where
      a.paddr =b.addr
      and a.last_call_et > 3600*3
      and status='INACTIVE'
    order by last_call_et
    /
   
    select 'kill -9 '||b.spid
      from v$session a, v$process b where
      a.paddr =b.addr
      and a.last_call_et > 3600*3
      and status='INACTIVE'
    order by last_call_et
    /
   
 use the first spool file..for db sessions kill..and run that 3-4 times
   
Then use the 2nd spool file..to terminate the processes at os level