RE: latch wait - cache buffer chain - Solved?

Maybe, ...maybe you were encountering some unlucky hash collisions. When two or more popular blocks hash to the same cache buffers chain (cbc), you end up with a higher amount of cbc latch competition than you want. It might be that when you created your new index, the file ids and block ids of the new index didn't hash to the same cache buffers chains as your old ones, and you removed an unlucky contention.

Problem is that now you'll never know, unless you still have the old index lying around. You could have looked in x$bh to see if you had pairs (or more) of particularly active blocks on the same cbc.

Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
Nullius in verba  

Hotsos Symposium 2007 / March 4-8 / Dallas Visit www.hotsos.com for curriculum and schedule details...

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

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of genegurevich_at_discoverfinancial.com
Sent: Thursday, October 26, 2006 10:56 AM To: oracle-l_at_freelists.org
Subject: Re: latch wait - cache buffer chain - Solved?

I seem to have solved my issue by building another index and the same query
that was not coming back
and running for 30min with a suppressed index is running in 3 to 4 minutes
now. What I wonder now is whether
this was a good solution in the long run or did I just do a bandage without
addressing the core issue. If anyone
have any thoughts I would appreciate them

In the meantime, thanks to Goran, Frits, Mark , Thomas and Eagle fan for thier help

thank you

Gene Gurevich
Oracle Engineering
224-405-4079  

             "Thomas Day"

             <tomday2_at_gmail.co

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Subject

                                       Re: latch wait - cache buffer
chain 
             10/25/2006 01:39

             PM

 

 

             Please respond to

             tomday2_at_gmail.com

 

 

I just look up "Ask Tom" and he says that there's only one reason to used a
reversed index -

"why you would: you are using OPS and need to remove a hot spot from an index on a table every node inserts into. Period. thats the only reason."

So I guess that it wouldn't be a worthwhile fix to this problem anyway.

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http://www.freelists.org/webpage/oracle-l Received on Thu Oct 26 2006 - 23:39:16 CDT