FreeLists / oracle-l / Re: How accurate is ADDM?

["John Kanagaraj" <john.kanagaraj@xxxxxxxxx>]

>   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:

We will have to remember that Advisors go by some internal rules that
we are not privy to. Generally, I use ADDM to help point to the
starting place, and I keep in mind that this is  working off
*instance* level stats for an hour. So, there are some pointers that
make sense and others that don't..... In this case, looks like you
selected one that makes sense, i.e. average disk response.

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

You mentioned that these were 30 spindles presented as one LUN.
Usually, this is achieved by another software layer on top which
"consolidates" these disk partitions, and this layer could be the
source of your issue. Your storage team may be looking at the SAN
stats - this may be reflected at that level. Another issue could the
SAN switches and HBA (Host Bus Adapters). There are a number of layers
that all need to work well together and the issue could be anywhere.
So what is your Storage virtualization layer?

-- 
John Kanagaraj <><
DB Soft Inc
http://www.linkedin.com/in/johnkanagaraj
http://jkanagaraj.wordpress.com (Sorry - not an Oracle blog!)
** The opinions and facts contained in this message are entirely mine
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