JWColby
jwcolby at colbyconsulting.com
Tue Feb 13 13:58:09 CST 2007
Arthur, I assume that you are discussing connections to SQL Server, not connections to an MDB BE? John W. Colby Colby Consulting www.ColbyConsulting.com -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of artful at rogers.com Sent: Tuesday, February 13, 2007 2:50 PM To: Access Developers discussion and problem solving Subject: Re: [AccessD] Number of users in the DB 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 -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com