select s.sid, s.serial#, t.start_time, t.xidusn, s.username
from v$session s, v$transaction t, v$rollstat r
where s.saddr = t.ses_addr
and t.xidusn=r.usn
and ((r.curext = t.start_uext-1)
or ((r.curext = r.extents -1) and t.start_uext=0))
/

SID    serial#    Start_Time      Xidusn      Username
-----------------------------------------------------
  9          27      2003/2/21          2                scott


블로킹 세션 제거하기

alter system kill session '9,27';