[AccessD] Number of users in the DB

artful at rogers.com artful at rogers.com
Tue Feb 13 13:49:53 CST 2007


The number of connections is typically several times the number of users. Of course this would depend on how you design the app, but let's just assume that your forms are bound and that each form contains a few combo-boxes, and that a given user has several forms open simultaneously. You may well get a connection for each combo on a form, plus the RecordSource of the form itself, so a given user might conceivably have 20 connections. 

I have tried and so far been unsuccessful at deducing the precise number of connections that any given user might have open. That's probably because I always used an existing app rather than one designed to elucidate this question. But one useful thing you might wish to try while running an ADP:

Open a window in Query Analyzer and run sp_who. That will list the connections to the selected database at the moment you execute it. You typically will find at least two or three connections per user.

Arthur 



----- Original Message ----
From: Dan Waters <dwaters at usinternet.com>
To: Access Developers discussion and problem solving <accessd at databaseadvisors.com>
Sent: Tuesday, February 13, 2007 1:47:39 PM
Subject: Re: [AccessD] Number of users in the DB


John,

How did you count the number of connections?  Was this equal to the number
of users?  

The local machine age being a strong factor makes sense since the BE machine
doesn't do any processing.

Great data! 

Dan Waters

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of JWColby
Sent: Tuesday, February 13, 2007 11:41 AM
To: 'Access Developers discussion and problem solving'
Subject: [AccessD] Number of users in the DB

There was a thread last week regarding the response times of the FE as the
number of users in the db went up.  Since all users complain about response
times, and since I belong to the set of developers with users, I decided to
look at this issue at one of my clients.  

The client runs systems from old 800mhz (I believe) Dells to modern 3ghz
Dells.
The client recently upgraded all switches to 1gbit.
The file server hosting the BEs is a fairly modern (2 GHz?) machine.
The FORM being opened is extremely complex.  It is bound, with tabs
I can get more complete statistics on the hardware.

The machine with the fastest access should be thrown out for statistics
because she does her work mostly in the early morning when there are no
users so the results would be misleading.

What I discovered:

The Min time to open can be misleading since the time of day when they
arrive, and thus how many users are already in the database will vary from
user to user.  I added the Min() user count and the Max() user count to
discover the extremes.
The Max time to open though is very instructive, but it needs to be compared
to the average as well.  The Max in this data appears to be an aberration,
which I do not have an answer for, but has never been repeated.
This data covers one complete day (yesterday).
This specific client had a maximum of 33 connections to the main database BE
open at once.
The minimum appears to be related to machines left on and in the database
overnight.

1) The second fastest user has an average time to open of .90 with a Max
time to open of 1.28.  Notice though that by the time the user started work,
the number of users was quite high.
2) The second slowest user has an average of 4.75 seconds to open with a max
of 7.88 seconds.
3) The times between are a pretty smooth gradient as the times climb from
slowest to fastest.
4) There is a startling difference between the fastest and slowest.
5) There is a definite correlation between the number of users and the times
to open
6) The number of users plays much less of a part than other factors

In talking to the client, it appears that the radical speed differences
between machines is largely dependent on the age of the machine, which
equates to the speed of the processor / memory / disks etc.  

In summary, I think it is safe to say that even given the small(?) maximum
number of concurrent users (33) the number of connections definitely impacts
the time to open the form.  OTOH, the impact seems to be much less than (in
fact dwarfed by) the impact of the age of the hardware.

It would be interesting to see how the numbers scale when the number of
users climbs up towards 100.  I will see if I can emulate that by opening
the BE directly over and over in separate instances of Access on my
workstation there.

Anyone desiring to see the totals query behind my results, please email me
offline and I will send it in a spreadsheet.


John W. Colby
Colby Consulting
www.ColbyConsulting.com

-- 
AccessD mailing list
AccessD at databaseadvisors.com
http://databaseadvisors.com/mailman/listinfo/accessd
Website: http://www.databaseadvisors.com

-- 
AccessD mailing list
AccessD at databaseadvisors.com
http://databaseadvisors.com/mailman/listinfo/accessd
Website: http://www.databaseadvisors.com


More information about the AccessD mailing list