RE: How accurate is ADDM?

You're looking at the average to write a particular file.

They are *probably* looking at the average service time of all requests.

SAME layouts rarely exhibit hot spots or overall average bad service statistics. Cary wrote a paper about it, and I like to keep in mind the old joke about the guy with one foot in boiling water and the other foot in a block of ice. His average of 122 degrees F was a comfortable hot tub!

Regards,

Mark W. Farnham

PS: BORING tends to make it easier to see if you have an actual problem with i/o, but is rarely as flat in i/o profile as SAME. Of course flat is not the same as fast, now is it?

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Best, David
Sent: Tuesday, December 04, 2007 3:21 PM To: oracle-l_at_freelists.org
Subject: How accurate is ADDM?

Hey all,

  How accurate is ADDM? Today we had a severe performance issue with one our of databases. The ADDM recommendation for that period put the most weight on the following:

---[ADDM Snip]---

Action Investigate the possibility of improving the performance of I/O to the online redo log files.  

Rationale The average size of writes to the online redo log files was 932 K and the average time per write was 3020 milliseconds.
---[ADDM Snip]---

The problem is, our storage team doesn't see the same level of degredation. Any suggestions?

tnx
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http://www.freelists.org/webpage/oracle-l Received on Wed Dec 05 2007 - 13:41:25 CST