Dan,

As I read the section of the Interbase Configuration Parameters document
concerning Database Cache size, it seems to address changes to the db. So, I
gather that "writes" refers to updating the db.

My concern when conducting Web application testing is with "reads" as well
as "writes". Can a dynamically served, "read" data page be cached, so that
if the page is requested again in the future, it is served from the cache
rather than going back to the copy on disk, executing the SQL query and
retrieving it again? To put it another way, if the Web application forms a
SQL query, will the Firebird/Interbase database engine first look in cache
memory for the requested data? Or does caching apply only to uncommitted
"writes"?

tks,

jwc


-----Original Message-----
From: Daniel Rail [mailto:daniel@...]
Sent: Friday, August 23, 2002 3:02 PM
To: ib-support@yahoogroups.com
Subject: RE: [ib-support] Data Caching by IB


At 23/08/2002 03:34 PM, you wrote:

>I plan to use InterBase as my data server. Early testing with WebHub

using

>the BDE and a Paradox database indicates a slight increase in response

time

>when different data are requested on two alternating data queries, but

have

>no idea if that approach actually defeated caching. To run this back to
>ground truth requires knowing how caching works, how many copies of data

can

>be cached, etc. Better would be to just turn off caching.

Did you try by assigning a database cache of 1 page? The cache size can
be
assigned for the server(ibconfig file) or at the database level(using
gfix).

>I'm still not certain of the relationship of caching to the "writes" that
>you mentioned below.
>
>If you can point me to a source where caching, synch/asynch writes and
>forced writes are explained I would be grateful.

Take a look here: http://www.ibphoenix.com/ibp_config.html

>Could you also pease confirm if "asynchronous writes" are the same as
>"forced writes".

Forced Writes ON will write the data to disk as soon as there's a
change. Forced Writes OFF, by definition, will write the data to disk
when
the system is idle, but under Windows this is performed only when all of
the connections are disconnected. Your database could start with 3MB in
size and insert 3GB and never see the physical size increase until all
connections are disconnected. To my knowledge, the problem doesn't exist
on the other platforms(OS).

>Does Win2k Pro support Forced Writes?

Yes.

>What I get from your message is that
>Forced Writes are equivalent to synchronous writes, and disabling forced
>writes amounts to setting asynchronous writes. If you could connect this
>terminology to the description of caching that I gave above, that would

be

>very helpful.

Your analogy is correct.


Daniel Rail
Senior System Engineer
ACCRA Group Inc. (www.accra.ca)
ACCRA Med Software Inc. (www.accramed.ca)


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