How oracle determine the value of optimal_size and onepass_size to use during pga_aggregate_target
- From: "Harvinder Singh" <Harvinder.Singh@xxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 16 May 2007 16:06:14 -0400
Hi,
I am trying to understand the algorithm used by Oracle when using
pga_aggregate target and it looks like to get the information on
Expected_WorkAreaSize, Oracle already knows about the value of
optimal_size(cache size) and onepass_size so I was wondering how oracle
calculate this values. Also in the same white paper it is mentioned that
to sort the 10GB of input data Oracle only needs about 40MB for 1 pass
but I thought to sort 10gb using 40MB bucket we need lot of passes so
how it calcuate this 40MB for onepass.
Thanks
--Harvinder
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