Message-ID: <10049.208.177.140.5.1215468573.squirrel@webmail.dannorris.com>
Date: Mon, 7 Jul 2008 15:09:33 -0700 (PDT)
Subject: received more blocks than served?
From: dannorris@dannorris.com
To: oracle-l@freelists.org
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Reply-to: dannorris@dannorris.com

I have a 3-node 10.2.0.3 RAC cluster on RH4. I was looking for
verification that I hadn't dropped any blocks between instances during GC
operations. So, I wanted to get a sum of all blocks sent, a sum of all
blocks received and they should be very close to equal.

What I see below has me perplexed. How can there be more blocks received
than served? That is, how can an instance receive more information than
was sent? Can a single block be served to multiple destinations? I don't
think so, but maybe that's where the magical block synthesis is coming
from?

It's a 3-node cluster, so there's no easy 1-to-1 mapping to be done.

I'm open for ideas...

  1  select sum(b2.value) "GCS CURR BLOCKS RECEIVED",
  2  sum(b1.value) "GCS CURR BLOCKS SERVED",
  3  (sum(b1.value)-sum(b2.value)) "SERVED - RECEIVED"
  4  from gv$sysstat b1, gv$sysstat b2
  5  where b1.name = 'gc current blocks served'
  6  and   b2.name = 'gc current blocks received'
  7* and   b1.inst_id = b2.inst_id

GCS CURR BLOCKS RECEIVED GCS CURR BLOCKS SERVED    SERVED - RECEIVED
------------------------ ---------------------- --------------------
	       628072519	      622037942 	    -6034577

Dan


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