text: SELECT ses.sid, ses.serial#, ses.osuser, ses.process
     FROM v$session ses, v$sess_io sio
    WHERE ses.sid  = sio.sid
      AND nvl(ses.username,'SYS') not in ('SYS', 'SYSTEM')
      AND sio.physical_reads = (SELECT MAX(physical_reads)
                                  FROM v$session ses2, v$sess_io sio2
                                 WHERE ses2.sid = sio2.sid
                                   AND ses2.username
                                    NOT IN ('SYSTEM', 'SYS'))
  /
  