History of top sessions!

Hi,

I am looking for the history of top sessions as it may give which session consuming more CPU or  I/O at particular time!..     Is there a way I will get that information beside Oracle Enterprise Manager. With the below script,  I will get current top sessions with high CPU, but I need session history with high CPU.

Your early response is very much appreciated.

===

SELECT
   s.username,
   t.sid,
   s.serial#,
   SUM(VALUE/100) as "cpu usage (seconds)"
FROM
   v$session s,
   v$sesstat t,
   v$statname n
WHERE
   t.STATISTIC# = n.STATISTIC#
AND
   NAME like '%CPU used by this session%