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Mon, Jun 4 2007 1:13 AM | Permanent Link |
Kerry Neighbour | I am using DBSAIM 4.25 build 4 with Delphi 7. I have an application that can connect to a database via Remote or Local settings - ie to a mapped drive path or to a DBISAMServer. The DBISAMServer connection works just fine. The Local connection does not. The problem is complicated, but it was reported by a customer, and I have confirmed the problem here. The problem is that one user can connect to a database with no problems. When a second user connects, the first user becomes VERY slow. The second user also slows down. Even is User B disconnects, USer A remains slow. User A has to quit and restart to get back to his normal speed. This is on a local network. User A is on one computer. User B is on another computer. The database is on yet another computer and that path is mapped to a common drive (ie something like G:\dbisam\data). Each user runs the application on the local machine, and simply points to the mapped database path. To give you some actual figures, here are some measured times User A starts up - runs the query : 26 seconds User B starts up (do not do anything, do not run query, but connect using DBISAMDatabase) User A runs same query again - query is now 90 seconds! User B quits. User A runs same query again - still 90 seconds User A quits. Then starts again. User A runs same query again - back to 26 seconds I tried this with DBSYS, and it does not have the same problem. Which is good - it means that it is something that I can probably fix! What I do im my application is use a single DBISAMDatabase component, connected to a DBISAMSession component. Everything else simply connects to these components. Nothing unusual, I would think. With this same application, I can connect to a remote DBISAMServer with no problems - ie it does not have this problem (as you would expect). One funny thing is that once User A slows down, it stays slow. Which is weird. Simply disconnecting the DBISAMDatabase component does not fix the problem. You actually have to quit the application. Anyone have any ideas about what I could try? |
Mon, Jun 4 2007 1:35 AM | Permanent Link |
Kerry Neighbour | One thing I note from looking at DBSYS is that you do not use a Session component
when you connect to a Local database. You use the internal .Session value. But then, you do not use a DBISAMDatabase component either. I use a DBISAMDatabase component (on the Datamodule form), connected to a DBISAMSession component. I simply switch the Session component from Local to Remote as required. This works, but could this be the cause of the speed issue? |
Mon, Jun 4 2007 1:35 AM | Permanent Link |
Kerry Neighbour | One thing I note from looking at DBSYS is that you do not use a Session component
when you connect to a Local database. You use the internal .Session value. I use a DBISAMDatabase component (on the Datamodule form), connected to a DBISAMSession component. I simply switch the Session component from Local to Remote as required. This works, but could this be the cause of the speed issue? |
Mon, Jun 4 2007 1:35 AM | Permanent Link |
Kerry Neighbour | One thing I note from looking at DBSYS is that you do not use a Session component
when you connect to a Local database. You use the internal .Session value. I use a DBISAMDatabase component (on the Datamodule form), connected to a DBISAMSession component. I simply switch the Session component from Local to Remote as required. This works, but could this be the cause of the speed issue? |
Mon, Jun 4 2007 2:48 AM | Permanent Link |
Roy Lambert NLH Associates ![]() | Kerry
If you search these newsgroups you'll find a number of posts about this issue. Essentially its down to Windows. Memory says its how Windows treats file locking. One user and its not a problem two or more and the file locking issue kicks in. The good news is that the performance slowdown after the second user is low. I can't remember is there was any solution posted. Sorry. Roy Lambert |
Mon, Jun 4 2007 2:44 PM | Permanent Link |
Tim Young [Elevate Software] Elevate Software, Inc. ![]() | Kerry,
<< The problem is that one user can connect to a database with no problems. When a second user connects, the first user becomes VERY slow. The second user also slows down. Even is User B disconnects, USer A remains slow. User A has to quit and restart to get back to his normal speed. >> What you're seeing is opportunistic locking in action. The speed when both users are connected is the real network speed. The speed with only one user connected is an "exclusive" mode access which uses caching and does not actually represent reality. http://www.elevatesoft.com/bulletin_6.htm -- Tim Young Elevate Software www.elevatesoft.com |
Mon, Jun 4 2007 7:23 PM | Permanent Link |
Kerry Neighbour | >
> What you're seeing is opportunistic locking in action. The speed when > both users are connected is the real network speed. The speed with > only one user connected is an "exclusive" mode access which uses > caching and does not actually represent reality. > > http://www.elevatesoft.com/bulletin_6.htm > Thanks for the heads-up. I have tried the registry changes mentioned by Microsoft, but they do not seem to do anything. It seems a real problem and not one easily solved. It is a real selling point for the client/server version, of course. |
Mon, Jun 4 2007 8:01 PM | Permanent Link |
"Robert" | "Kerry Neighbour" <kerry@dojitraders.com> wrote in message news:639022cae2cf8c97569f5a454ce@elevatesoft.com... >> >> What you're seeing is opportunistic locking in action. The speed when >> both users are connected is the real network speed. The speed with >> only one user connected is an "exclusive" mode access which uses >> caching and does not actually represent reality. >> >> http://www.elevatesoft.com/bulletin_6.htm >> > > Thanks for the heads-up. I have tried the registry changes mentioned by > Microsoft, but they do not seem to do anything. It seems a real problem > and not one easily solved. > It's unsolvable. When you only run one user, M$ knows not to bother with all the checking necessary to process multi-user correctly, and your program runs much faster. I hate to admit it, but it was a clever feature on the part of M$, since there are many single-user applications running on servers. But of course the moment you have more than one user, you lose that advantage. > It is a real selling point for the client/server version, of course. My experience is that DBISAM CS is not that much faster until you get to a fairly large number of concurrent users. But I'm sure it depends on the application. Robert > |
Mon, Jun 4 2007 10:54 PM | Permanent Link |
Gregory Sebastian | Hi Kerry
Kerry Neighbour <kerry@dojitraders.com> wrote: <<One thing I note from looking at DBSYS is that you do not use a Session component when you connect to a Local database. You use the internal .Session value. But then, you do not use a DBISAMDatabase component either. I use a DBISAMDatabase component (on the Datamodule form), connected to a DBISAMSession component. I simply switch the Session component from Local to Remote as required. This works, but could this be the cause of the speed issue?>> Just curious but where does your PrivateDir in the session component point to ? Does it point to a local path or to the network folder. If the same query under the same conditions runs much faster on DBSys then on your app then this could be the problem. regards gregory |
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