Performance issue High disk I/O

Question

Hi All,
we have Oracle9i Enterprise Edition Release 9.2.0.1.0 - Production running on REd Hat EE 4
We are having some high disk I/O issues after doing some schema changes last week.
I checked some wait events but found pmon timer and smon timer at the top all the time. but not getting any clue of reason behind it.
If anyone has faced such issue then please advice as what could be reason of it.
SELECT a.SID, a.event, a.wait_time, a.seconds_in_wait, a.state
FROM v$session_wait a, v$session b
WHERE a.SID = b.SID AND event <> 'SQL*Net message from client'
ORDER BY seconds_in_wait DESC
SID     EVENT     WAIT_TIME     SECONDS_IN_WAIT     STATE
1     pmon timer     0     4090     WAITING
8     smon timer     0     1209     WAITING
9     rdbms ipc message     0     799     WAITING
regards
vinay

Answer 1

To add some more information to this
The disk activity before doing schema changes used to be somewhere around 30-45% but now it has suddenly went to 70-80%.
The schema changes includes addition of some complex views, tables and indexes.
but i haven't seen any considarable chnages in size of newly added objects they are all together less than 1.5 gb and our total database size is 700GB.
i took snapshot for over period of time i found top event as direct path write
Top 5 Wait Events
~~~~~~~~~~~~~~~~~ Wait % Total
Event Waits Time (cs) Wt Time
direct path write 1,444,566 495,020 38.06
direct path read 677,912 139,936 10.76
PX Deq: Execution Msg 1,252 129,432 9.95
db file scattered read 1,235,215 117,431 9.03
db file sequential read 912,288 98,714 7.59
Top 5 Wait Events
~~~~~~~~~~~~~~~~~ Wait % Total
Event Waits Time (cs) Wt Time
direct path write 3,923,608 1,218,268 33.98
db file scattered read 1,770,687 533,507 14.88
direct path read 3,676,295 468,525 13.07
db file sequential read 1,911,892 331,635 9.25
SQL*Net more data to client 7,126,163 188,606 5.26
there is considerable slow response has been reported on application but but still usable.
Regards
Vinay