You can check SQL Memory Management in Oracle9i
http://www.cs.ust.hk/vldb2002/VLDB2002-proceedings/papers/S29P03.pdf
and search google for other papers by both authors of this paper.
Don't know whether you'll get exactly this information but article was
really interesting :)

Gints Plivna
http://www.gplivna.eu

2007/5/16, Harvinder Singh <Harvinder.Singh@(protected)>:
> 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.
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