Oracle database final_blocking_session when we have multiple blocking sessions

When  there are multiple blockings in database  its confusing to gind  actual blocking .  Oracle has simplified it by   final_blocking_session .

final_blocking_instance:  This column of gv$session is the instance identifier of the final blocking session. This column is valid only if final_blocking_session_status=valid.

final_blocking_session:  This column of gv$session is the session identifier of the final blocking session. This column is valid only if final_blocking_session_status=valid.

exec dbms_output.put_line('========== Session Details ==========');

set feedback on

set lines 300

set pages 1000

column TERMINAL format a30

column USERNAME format a15

column OSUSER format a20

column MACHINE format a20

column PROGRAM format a30

select inst_id,sid,FINAL_BLOCKING_SESSION ,final_blocking_instance ,serial#,username,osuser,machine,terminal,program,status,to_char(logon_time, 'dd-mon-yy hh24:mi:ss') , event, blocking_session , sql_id 

from gv$session 

where FINAL_BLOCKING_SESSION_STATUS='VALID'   or blocking_session is not NULL

order by LOGON_TIME,machine,program;

set pages 1000

set lines 120

set heading off

column w_proc format a50 tru

column instance format a20 tru

column inst format a28 tru

column wait_event format a50 tru

column p1 format a16 tru

column p2 format a16 tru

column p3 format a15 tru

column Seconds format a50 tru

column sincelw format a50 tru

column blocker_proc format a50 tru

column fblocker_proc format a50 tru

column waiters format a50 tru

column chain_signature format a100 wra

column blocker_chain format a100 wra

SELECT * 

FROM (SELECT 'Current Process: '||osid W_PROC, 'SID '||i.instance_name INSTANCE, 

 'INST #: '||instance INST,'Blocking Process: '||decode(blocker_osid,null,'<none>',blocker_osid)|| 

 ' from Instance '||blocker_instance BLOCKER_PROC,

 'Number of waiters: '||num_waiters waiters,

 'Final Blocking Process: '||decode(p.spid,null,'<none>',

 p.spid)||' from Instance '||s.final_blocking_instance FBLOCKER_PROC, 

 'Program: '||p.program image,

 'Wait Event: ' ||wait_event_text wait_event, 'P1: '||wc.p1 p1, 'P2: '||wc.p2 p2, 'P3: '||wc.p3 p3,

 'Seconds in Wait: '||in_wait_secs Seconds, 'Seconds Since Last Wait: '||time_since_last_wait_secs sincelw,

 'Wait Chain: '||chain_id ||': '||chain_signature chain_signature,'Blocking Wait Chain: '||decode(blocker_chain_id,null,

 '<none>',blocker_chain_id) blocker_chain

FROM v$wait_chains wc,

 gv$session s,

 gv$session bs,

 gv$instance i,

 gv$process p

WHERE wc.instance = i.instance_number (+)

 AND (wc.instance = s.inst_id (+) and wc.sid = s.sid (+)

 and wc.sess_serial# = s.serial# (+))

 AND (s.inst_id = bs.inst_id (+) and s.final_blocking_session = bs.sid (+))

 AND (bs.inst_id = p.inst_id (+) and bs.paddr = p.addr (+))

 AND ( num_waiters > 0

 OR ( blocker_osid IS NOT NULL

 AND in_wait_secs > 10 ) )

ORDER BY chain_id,

 num_waiters DESC)

WHERE ROWNUM < 101;