Who is blocking me?

col username for a25
col IS_BLOCKED_BY for a20
col state for a40
col sql_id for a15
col obj for a80
set lines 220
set trim on

select
  nvl(USERNAME,schemaname)||' ('||SID||':'||INST_ID||')' USERNAME
 ,SQL_ID
 ,nvl2(BLOCKING_SESSION,BLOCKING_SESSION||':'||BLOCKING_INSTANCE||':'||
   (select
      sql_id
    from
      gv$session holder
    where
      holder.inst_id= s.BLOCKING_INSTANCE
    and holder.sid=s.BLOCKING_SESSION), null) IS_BLOCKED_BY
 ,decode(state, 'WAITING', 'WAITING', 'ON CPU')||'
 ('||substr(event,1,40)||')' state
 ,ROW_WAIT_FILE#||':'||ROW_WAIT_BLOCK#||':'||ROW_WAIT_ROW#||'
'||case
    when ROW_WAIT_OBJ# >0 then
     (select owner||':'||object_name||':'||nvl(subobject_name,'=nosub=')||' ('||object_type||')'
      from
       dba_objects do
      where
       do.object_id=s.ROW_WAIT_OBJ#)
  end obj
from
  gv$session s
where
  event in
    (select
       NAME
     from
       v$event_name
     where
       WAIT_CLASS != 'Idle')
order by sid;