September 1, 2005 at 10:41 pm
Hi all,
We developed an application using Visual Foxpro 8.0 in the frontend and MS SQL Server 2000 at the backend. The VFP uses an ODBC connection to connect to data in SQL Server. We have about 30-40 users using the application in the office.
Occasionally (e.g. twice a day, or once a week) the user will see the following error in their client computer:
[Microsoft][ODBC SQL Server Driver]Communication Link Failure
The user needs to exit the application and log on again, and then everything goes fine. We are just using typical office LAN connection. When the problem occurs, only one user will find the error. Other users are not having any problems.
There is no error in the SQL Server logs or Windows Event Logs, but when I run sp_monitor there will be a non-zero value in the packet_errors field. Some of our user uses older Windows, like Windows 98 or Windows ME.
(1) How can we troubleshoot this error? (from SQL Server, from network health check)
(2) How to prevent this error?
(3) If it's a network problem, will it likely be at the server side or client side?
Any help or suggestion will be much appreciated.
September 5, 2005 at 8:00 am
This was removed by the editor as SPAM
September 5, 2005 at 12:42 pm
Might be completely unrelated, but when a particular printer mentioned an error it caused to block all tcp/ip sockets, resulting in communication link failures, no internet ...
A thing that helped was restarting the print spooler service.
September 6, 2005 at 1:24 pm
FoxPro originally was a desktop database engine for small stand-alone applications (like Access, FireBird, Paradox, etc.). Now it is being used as a communications front-end to SQL Server in some instances - a LAN application. This is going to cause issues from the smallest of hiccups in the network - which I believe that you are now seeing. Believe me I know, I've got a couple of vendor apps serving about a dozen users that used to mis-behave this way.
First things to check are NIC card settings on the SQL Server and the Switch. They should match - e.g. 100mb/Full Duplex --> NOT 'auto'
Then check the NIC card settings on the client PC's and their associated switch ports. The too should aregg - e.g. 10mb/Half Duplex or 10mb/Full duplex --> again, NOT 'auto'
Be wary, dependent on the OS of your server and desktops a restart may be needed for the NIC card setting to take full affect. Also, the switch port setting (when they are changed) will cause a very brief connectivity outage, so try this afgter hours.
Above all, you'll need to take your network engineer to lunch or something (bribery), because if the NIC and switch settings do not help, you'll need him to assist possibly with a 'sniffer'.
RegardsRudy KomacsarSenior Database Administrator"Ave Caesar! - Morituri te salutamus."
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