On Mon, Sep 19, 2011 at 10:41 AM, Marcelo Caetano <marcelo@...>wrote:

> I have a Firebird 2.5 server running in a Windows Server 2008 64bit. The
> server have 16 cpu cores and 16GB of RAM. The database file have 3099MB of
> size and I have 2% of writes against 98% of reads of all I/O requisitions.
> How can I put the entire database (or the most part) in memory by adjusting
> the Page Size, Cache Size and the DefaultDbCachePages parameter? Is it
> possible?
>
>

Sean is right that Windows will hold the working portions of the database in
its page cache which may well be more effective than using database cache.
Others are right that you could use a RAM disk - though the page cache
solutions have the advantage of writing changes to disk, so you don't risk
losing that 2% of your operations if the RAM disk fails. However, there's
also a simple, if unnecessary, answer to your question.

Figure out how big your database is, leaving room for expansion, divide that
number by your page size and the result is the number of pages in the
database, give or take Window's file size measurements, and that should be
your cache size.
By allocating that much memory to the database page cache, you reduce the
amount of memory available for other uses, like the system page cache.

Typically databases have a working set of data which is in regular use and
other data that is referenced less often. You're likely to get best
performance if you let the database page cache and the system page cache
decide which pages are frequently used and should be kept in memory and
which can rest quietly on disk, not wasting valuable RAM space. If you're
even considering keeping the whole database in memory, run 64-bit Firebird.
The MON$ tables that report on fetches/reads/writes/marks will give you a
clue about the effectiveness of the cache.

Good luck,

Ann


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