We are having an annoying intermittent problem where database connections from our client application on a variety of stations will get dropped. We have applications that use ODBC, Borland Database Engine, and ADO and all get dropped. When connections do get dropped, it isn't everyone - some remain connected while others get dropped. Looking in the logs of one of the applications, I see messages like the following:

  • TCP Provider: The semaphore timeout period has expired
  • TCP Provider: An existing connection was forcibly closed by the remote host
  • Query timeout expired
  • TCP Provider: No such host is known

I don't see any error messages in the SQL error log or in the Windows events on either the client or the SQL Server. Is there anyway to determine if this is a database or network issue from the SQL Server side of things? For example, is there something I can turn on to monitor database connections and get reports when they are dropped? This happens maybe once or twice a day but not at any specific time (not when backups run or something).

The issue seems to be network related and out of scope for this forum.

  • Ask your network guys if there are any TCP/IP idle timeouts set on the firewalls.
    – Philᵀᴹ
    Mar 31 '14 at 13:33
  • @GrumpyPhil: We don't have any firewalls between the clients and the SQL Server other than the Windows Firewall on the client themselves.
    – Caynadian
    Mar 31 '14 at 13:41
  • @Caynadian and is the behavior any different if you entirely shut that thing off? (In other words, this is certainly sounding like a network connectivity issue, not a database problem.) Mar 31 '14 at 13:46
  • @AaronBertrand: I have it shut off on one particularly problematic machine and it still occurs. In fact, this machine (which is a VM running on VMware 5) experiences this issue more often than most though that might be because it runs 24-7 instead of just business hours. Is there any SQL Server specific network monitoring tools you can think of? I should note that the SQL Server is on a physical host and is not a VM.
    – Caynadian
    Mar 31 '14 at 13:57
  • It could be a physical problem with the cables. We had a customer with similar complaints about our software. Our IT guy flew to the customer location, replaced some Ethernet cables, and the problem went away. Mar 31 '14 at 15:09

It can be SQL related, not just OS and hardware:


  • Chris, try to provide actual content and not just link answers. Apr 17 '15 at 23:59
  • @Chris: Thanks for that but I didn't see any "non-yeilding" error messages in any of the logs. Regardless, it seems to have been a hardware issue as the DB server RAID array crashed and since we have rebuilt the server on a new platform, we haven't had any issues.
    – Caynadian
    Apr 20 '15 at 16:29

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