Subject Re: [firebird-support] SortMemBlockSize
Author Helen Borrie
At 04:17 PM 23/09/2004 +0200, you wrote:
>Hi all,
>trying to tune up the performance of FB 1.5, we have found
>parameters in the firebird.conf configuration file.
>They seem to be used for so called in-memory sorting (used belike by
>commands GROUP BY, ORDER BY...)
>What we really want to know is how these two parameters interact
>together and what is the ideal setting for them.

There is no "ideal" setting but the defaults (1 Mb block size, up to a
limit of 64 Mb) are determined to be "useful". If a sort needs more space
than 64Mb, it will create the sort files in your configured sort space on
disk. It will do that sooner if available RAM gets tight before it hits
the 64-block limit.

On SS, connections share sort space, so you can cheerfully allocate a
higher limit or a larger block size (or both) if you are currently
under-utilizing memory. If your sorts are currently using disk sort space,
you should notice the difference.

On Classic, each connection gets a static 8 Mb, because each has its own
sort space. It's going to take a smaller hike in block size or upper limit
to consume your spare resources.

>We are running FB under 64bit Linux (AMD Athlon) with 2GB RAM.

Lucky server. :-) Experiment!!