At 11:24 PM 6/06/2005 +0000, you wrote:

>Also, this is for FB SS 1.5.2 on WinXP Pro.
>
>Thanks
>--- In firebird-support@yahoogroups.com, "buppcpp" <buppcpp@y...>
>wrote:
> > When does the sort memory usage come into play?
> >
> > I have SortMemUpperLimit = 67108864 in my configuration, but my
>memory
> > usage never goes above my DefaultDbCachePages settings.
> >
> > I expected the max memory usage to be (DefaultDbCachePages * Page
> > Size) + SortMemUpperLimit when a SORT is involved. But I'm not
>seeing
> > it, so I'm assuming my understanding of SortMemUperLimit is
>incorrect.

The page cache and sort memory are unrelated. The engine doesn't use the
page cache for sorting.

With SS, page cache is dynamic, so you aren't going to see the effect of
max. cache unless the cache is "full".

As far as I understand it, sorts are done using dynamic memory from the OS,
if possible, up to the maximum specified in SortMemUpperLimit. However,
that doesn't necessarily mean a sort will be able to acquire that amount of
memory for a particular sort operation. If you have several large order
by's or group by's going on simultaneously and/or the OS is using a lot of
dynamic RAM for something else, someone is likely to cop either an on-disk
sort or RAM being paged out to disk cache during the course of an in-memory
sort.

> >
> > So, like I said, When does the sort memory usage come into play?

If possible, it's the first choice.

./hb