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@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Best, David
Sent: Tuesday, December 04, 2007 3:21 PM
To: oracle-l@xxxxxxxxxxxxx
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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