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The LAN which has about a half dozen windows xp professional pcs and one windows 7 professional pc.

A jet/access '97 database file is acting as the database.

The method of acccess is via dao (DAO350.dll) and the front end app is written in vb6. When an instance is created it immediately opens a global database object which it keeps open for the duration of its lifetime.

The windows 7 machine was acting as the fileserver for the last few months without any glitches.

Within the last week what's happened is that instances of the app will work for a while (say 30 mins) on the xp machines and then will fail on database operations, reporting connection errors (eg disk or network error or unable to find such and such a table. Instances on the windows 7 machine work normally.

Moving the database file to one of the xp machines has the effect that the app works fine on ALL the xp machines but the error occurs on the windows 7 machine instead.

Just before the problem became apparent a newer version of the app was installed. Uninstalling and installing the previous version did not solve the problem.

No other network changes that I know of were made although I am not entirely sure about this as the hardware guy did apparently visit about the same time the problems arose, perhaps even to do something concerning online backing up of data. (There is data storage on more than one computer) Apparently he did not go near the win 7 machine.

Finally I know not very much about networks so please forgive me if the information I provide here is superfluous or deficient.

I have tried turning off antivirus on the win 7 machine, restarting etc but nothing seems to work.

It is planned to move our database from jet to sql server express in the future.

I need some suggestions as to the possible causes of this so that I can investigate it further. Any suggestions would be gretly appreciated

UPDATE 08/02/2011

The issue has been resolved by the hardware guy who visited the client today. The problem was that on this particular LAN the IP addresses were allocated dynamically except for the Win 7 machine which had a static IP address. The static address happened to lie within the range from which the dynamic addresses were being selected. This wasn't a problem until last week when a dynamic address was generated that matched the static one and gave rise to the problems I described above.

Thanks to everyone for their input and thanks for not closing the question. Having smart knowledgeable people to call on is a great help when you're under pressure from an unhappy customer and the gaps in your own knowledge mean that you can't confidently state that your software is definitely not to blame.

kjack
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  • Before you close this I have been all over the internet without success on this, I know it's not got an easy answer I just need some guidance – kjack Feb 05 '11 at 23:44
  • Check the NETBIOS over TCP/IP setting on the server -- it must be OFF. It doesn't matter what the setting is on the workstations. – David-W-Fenton Feb 07 '11 at 00:01
  • +1 this question is programming-related. Please don't vote to close without leaving a comment. – MarkJ Feb 07 '11 at 15:46
  • @David, Thanks for the suggestion. Unfortunately I can't check anything at the moment as the 'problem computer' can no longer be accessed remotely. The client swapped it with another PC from the network that wasn't being used much and says is now getting errors about ip conflicts. He has the hardware guy visiting tomorrow to hopefully solve things. – kjack Feb 07 '11 at 22:50
  • @Mark Thanks for your support. I'll make sure to report how this finishes – kjack Feb 07 '11 at 22:54
  • @everyone I've edited the question, now that the problem has been fixed – kjack Feb 08 '11 at 21:19
  • I posted a related kind of problem in your other question on this. Most DHCP servers allow you to reserve IP addresses within the DHCP server's IP range so that you could then have fixed IP addresses like this one. It's almost never a good idea, but I recently did it on a LAN where there was a network printer with all the workstations pointing at the IP address, which happened to be static and was in the middle of the DHCP range. Excluding that in the DHCP server configuration fixed a host of problems. – David-W-Fenton Feb 09 '11 at 03:48
  • Thanks for responding with your problem fix. I've updated my corruptions symptoms page with your problem. – Tony Toews Feb 20 '11 at 05:21
  • You're welcome, I've just visited your website which I hadn't seen before, there's some great info there (very relevant to me), I've bookmarked it! – kjack Feb 20 '11 at 12:38

1 Answers1

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I'd try:

  • Validate that same DAO and ODBC-drivers is used on both xp- and vista machines.

  • Is LAN single broadcast domain? If not, rewire. (If routers required make sure WINS is working)

  • Upgrade to ms-sql. It could be just a day of well worth work, ;-)

regards, //t

Teson
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