Re: PGA_AGGREGATE_TARGET question

"Richard Foote" <richard.foote_at_bigpond.com> wrote in message news:qK5%a.35388$bo1.16629_at_news-server.bigpond.net.au...
> "Brian Peasland" <dba_at_remove_spam.peasland.com> wrote in message
> news:3F3B9C49.C992515D_at_remove_spam.peasland.com...
> > There are some nice views that help you in sizing PGA_AGGREGATE_TARGET
> > (P_A_T). If you size this parameter too high, then you will be wasting
> > memory, and if it is sufficiently high enough, this can cause swapping
> > to occur in your database server.
>
> Hi Brian,
>
> You mentioned above and elsewhere in your post that you will be wasting
> memory if you set PAT too high. Interested to know how you come to that
> conclusion as Oracle doesn't allocate the memory unless it's required. You
> can most certain set it too low and have sub-optimal workarea executions,
> you can most certainly see it way too low and have the sum of the
untunable
> components of the PGA exceed the PAT regardless and you can set it too
high
> such that you don't have enough memory to service such a target.

Hi Richard

I *believe* that whether or not Oracle pre-allocates PAT is platform dependent, I'm pretty sure that on Windows at least you get the memory up front.

-- 
Niall Litchfield
Oracle DBA
Audit Commission UK