Which is exactly the effect of having multiple threads which are not thread safe.
> QUOTE FROM > > http://support.microsoft.com/?scid=kb;en-us;303528 > > Additional best practices for network environments > > Microsoft Jet is a file-sharing database system. A file-sharing database > system means that the processing of the file occurs at the client. When a > file-sharing database, such as Microsoft Jet, is used in a multi-user > environment, multiple client processes use file read, file write, and file > locking operations on the same shared file across a network. If a process > cannot be completed, the file may be left in an incomplete state or in a > corrupted state. A process may not be completed for either of the > following > reasons: > > > . > > When a client is stopped unexpectedly > > > . > > When a network connection to a server is dropped > > Microsoft Jet is not intended for use with high-stress server > applications, > high-concurrency server applications, or 24 hours a day, seven days a week > server applications. This includes server applications, such as Web > applications, commerce applications, transactional applications, and > messaging server applications. For these types of applications, the best > solution is to switch to a true client/server-based database system, such > as > Microsoft Data Engine (MSDE) or Microsoft SQL Server. When you use > Microsoft > Jet in high-stress applications such as Microsoft Internet Information > Server (IIS), you may experience any one of the following problems: > > > . > > Database corruption > > > . > > Stability issues, such as IIS crashing or locking up > > > . > > Sudden failure or persistent failure of the driver to connect to a valid > database that requires re-starting the IIS service > > The following sections contain recommendations to follow when you share a > Microsoft Jet or a Microsoft Access database file on a network file > server. > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > On > Behalf Of Matthew Comb > Sent: Thursday, 16 March 2006 4:09 p.m. > To: NZ Borland Developers Group - Delphi List > Subject: RE: [DUG] List working? > > > > I've always felt like Access was like a multithreaded server without > > critical sections. > > > > With one user you will have absolutely no problems. With few users its > > highly unlikely that the threads will clash. > > > > With more users, it turns to a pile of crap, which can be addressed by > > having keepalives (rebuild mechanisms on startups and around the posting > > routines etc). > > > > But seriously. I can't accept that people would actually push access as a > > serious contender for multi user environments. > > > > I mean sure I could wash my clothes in the bath, but it doesn't make it a > > dual purpose washing machine, > > > > and if i was going to ride up a mountain, I could surely do it on a bike, > > but it would be a hell of a lot easier in a 4 wheel drive. Especially one > > strong enough to protect me from crazy random people on bikes descending > > down the mountain... > > > > > > > >> Well if we are talking a small multiuser system then it does have some > >> advantages. In my view those advantages are more than outweighed by the > >> potential for data corruption anytime a client freezes or disconnects >> from > >> the network, not to mention lack of Stored Procs etc (at least in the > >> version I used). That's why we use MSDE/SQL Server instead now. > >> > >> However that doesn't mean everyone would come to the same conclusion I > >> did. > >> For some people Access's advantages might be godsends. For example, I >> have > >> my doubts that our Christchurch customer is using the same server box >> that > >> they were using 8 years ago (they might be but it seems unlikely). That > >> means they have probably moved the database on their own without >> support. > >> With Access moving the database just means moving the mdb file and > >> creating > >> a new network share. I doubt they would have been able to move an MSDE > >> database without our help. Similarly backing up MSDE requires either > >> special > >> backup software or running a script to backup the data/log files to disk > >> and > >> then to your backup destination. Backing up Access is a simple matter of > >> copying a file. > >> > >> Access is also blindingly fast at accessing data which isn't changing. > >> Once > >> data has been cached locally it becomes near impossible for a proper > >> server > >> based database to compete in pure read speed terms. Of course if the >> data > >> being accessed is constantly changing then the situation reverses, etc. > >> > >> Just because most serious developers value the functionality of a server > >> based database more than the functionality Access provides doesn't mean > >> that > >> it is a completely useless product. > >> > >> All IMO of course. And should be taken with a grain of salt as I haven't > >> used Access for development since 1998... > >> > >> David. > >> > >> > >> > >> -----Original Message----- > >> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > >> On > >> Behalf Of Neven MacEwan > >> Sent: Thursday, 16 March 2006 3:45 p.m. > >> To: NZ Borland Developers Group - Delphi List > >> Subject: Re: [DUG] List working? > >> > >> David > >> > >> In my opinion a software product that doesn't meet very high reliability > >> levels in its designers intended use is a poor product, If you are > >> prepared to state that Access is a very reliable platform in multiuser > >> environments I'd be interested, otherwise you might as well suggest a > >> person with a stutter makes a very good news reader providing you listen > >> carefully > >> > >> Neven > >> > >> David Brennan wrote: > >>> We have a customer in Christchurch who has been running an old VB4 > >>> version > >>> of our software with multiple client machines connecting to an Access > >>> 2.0 > >>> (32 bit) database. They have been running the software for about 7 or 8 > >>> years. > >>> > >>> We tend to forget they are there... because they have never once called > >> with > >>> a problem of any sort. > >>> > >>> Not saying you are going to be that lucky every time and part of the > >> reason > >>> we don't hear from them may be that the program has startup code for > >>> attempting auto-recovery from corrupted databases. But Access <can> be > >>> surprisingly fast and reliable. > >>> > >>> David. > >>> > >>> > >>> -----Original Message----- > >>> From: [EMAIL PROTECTED] >>> [mailto:[EMAIL PROTECTED] > >> On > >>> Behalf Of Neven MacEwan > >>> Sent: Thursday, 16 March 2006 3:16 p.m. > >>> To: NZ Borland Developers Group - Delphi List > >>> Subject: Re: [DUG] List working? > >>> > >>> Don't be dim James are you saying that Access is not intended for DB > >>> applications, The assertion that its ok and was designed for "single > >>> user desktop style" apps and not anything more is crap if it wasn't > >>> intended for " multi user environment" then it shouldn'd effing well > >>> support it (badly or otherwise) should it? > >>> > >>> Neven > >>> > >>> James Sugrue wrote: > >>>> The problem isn't with Access, the problem is people using Access for > >>> things > >>>> it's not really intended for. > >>>> Access is fine - and I use it all the time - for single user desktop > >> style > >>>> applications. It's when it gets used in a multi user environment >>>> things > >>> can > >>>> be a problem, especially when combined with bad design or programming. > >>>> > >>>> > >>>> -----Original Message----- > >>>> From: [EMAIL PROTECTED] > >>>> [mailto:[EMAIL PROTECTED] > >>> On > >>>> Behalf Of Maurice Butler > >>>> Sent: Thursday, 16 March 2006 8:28 a.m. > >>>> To: 'NZ Borland Developers Group - Delphi List' > >>>> Subject: RE: [DUG] List working? > >>>> > >>>> Hi, > >>>> If you want to know how bad Mickysoft Access is ask any school that > >>>> runs > >>>> musac - this is a student manager program that spends more time being > >>> fixed > >>>> than used. > >>>> If you want sql, mdse is alright for small apps that need sql & > >>>> Mickysoft > >>>> compatablity. > >>>> > >>>> Maurice > >>>> > >>>> > >>>> > >>>> _______________________________________________ > >>>> Delphi mailing list > >>>> [email protected] > >>>> http://ns3.123.co.nz/mailman/listinfo/delphi > >>>> > >>>> > >>> > >> > >> -- > >> Neven MacEwan (B.E. E&E) > >> Ph. 09 620 1356 Mob. 027 4749 062 > >> > >> New Address Details > >> =================== > >> MWK Computer Systems > >> 1 Taumata Rd > >> Sandringham > >> Auckland > >> > >> Ph 620 1356 > >> Fx 620 1336 > >> > >> _______________________________________________ > >> Delphi mailing list > >> [email protected] > >> http://ns3.123.co.nz/mailman/listinfo/delphi > >> > > > > > > _______________________________________________ > > Delphi mailing list > > [email protected] > > http://ns3.123.co.nz/mailman/listinfo/delphi > _______________________________________________ > Delphi mailing list > [email protected] > http://ns3.123.co.nz/mailman/listinfo/delphi _______________________________________________ Delphi mailing list [email protected] http://ns3.123.co.nz/mailman/listinfo/delphi
