Oracle-L: RE: urgent: lots of db file sequential read

From: John Clarke <jclarke_at_centroidsys.com>
Date: Tue, 25 Feb 2003 19:18:45 -0800
Message-ID: <F001.005597C9.20030225191845@fatcity.com>

What's the average time/wait, since adding devices?

I think you should focus on time/event, not count/event.

Thanks.

-----Original Message-----
Sent: Tuesday, February 25, 2003 3:04 PM To: Multiple recipients of list ORACLE-L

hi, friends:
My db server has one poor t3(raid5, 256M Cache) and it is rather slow in disk io.
This night, I added a second T3(256M Cache,Raid10) to the database and moved half of datafiles to the second raid. But it seems from statspack, IO wait is more than before:

Statistic                                    Total   per Second    per

Trans

--------------------------------- ---------------- ------------
------------
CPU used by this session                    66,663         23.5
8.2
CPU used when call started                  66,692         23.5

8.2

------------ ------------
db file sequential read 225,846 178,026 93.03 log file sync 8,604 4,167 2.18 log file parallel write 8,665 3,593 1.88 db file parallel write 768 2,455 1.28

now: 66 cpu used /178 cpu waited.
But with the old configuration, cpu used vs cpu waited is like: old: 7832 cpu used / 17508 cpu waited

------------ ------------
db file sequential read 10,164,408 17,508,898 83.50 db file parallel write 46,130 1,072,257 5.11 enqueue 90,498 854,241 4.07

Statistic                                    Total   per Second    per

Trans

--------------------------------- ---------------- ------------
------------
CPU used by this session                 7,832,321        167.4
9.5
CPU used when call started               7,832,333        167.4

9.5

These snapshot are from different time and different time lengh, but I think after i added a disk array to disk array, IO wait should slowdown, but from the new statspack, relatively more time is spent on io wait? How to explain this?
Thanks.

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Author: John Clarke
INET: jclarke_at_centroidsys.com

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