received more blocks than served?

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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http://www.freelists.org/webpage/oracle-l Received on Mon Jul 07 2008 - 17:09:33 CDT