Parallel query on when it 's not supposed to be (?) 2004-09-15 - By Mladen Gogala
On 09/14/2004 10:03:10 PM, Mark Richard wrote:
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> I just wanted to pose a question to anyone on the list (particular the wait
> event guru 's like Cary)...
Event guru? That 's what Cary is? Hmmm, not exactly the expression
that I 'd use.
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> Eliminating parallel query because you are seeing waits for it sounds to me
> a little like tuning the BCHR. I can 't help but wonder if waiting for a
> parallel query is still the quickest way to get things done? Would killing
> the parallel query effectively move the waits to another category without
> achieving any real gain?
If the instance is OLTP with several hundreds of concurrent users, you definitely
don 't want PQ utilized by users, on regular basis, because it would quickly
drain your machine resources. If a full table scan somehow makes it into production,
and it happens even to the best of us, then you want to minimize the damage and
not resolve it by devoting enormous resources to it, thus starving everybody
else of CPU power. PQ is not a magic potion thad druid Getafix used to cook
(I apologize to my American friends who have never heard of Asterix and Obelix)
to increase power of the tiny Gaul warrior, PQ is a tool that has its place,
primarily in the batch and DW systems. Enabling PQ on a busy OLTP instance is
something that can be compared to another French comic, namely Gaston. There are
many French speaking people on this list, they may explain to you everything
about Gaston Lagaffe.
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Mladen Gogala
Oracle DBA
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http://www.freelists.org/webpage/oracle-l
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