A network-related or instance-specific error

Question

We have two servers one is sharepoint server and another one is SQL server. There is still disk space available on both the sharepoint web and the sql server, but it seems like the web server can't connect to the SQL server.

It seems to be flapping... meaning it'll work, then drop, then work, etc. Today we get continous error in ULS log:A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections in sharepoint.

Answer 1

Some ideas for further troubleshooting:

• Check SQL-Server logs if there is an error in your SQL-Server.
• Use HRPing and continously ping from SharePoint to SQL Server to find out if network connectivity disappears.
• Use tcping to check if SQL-Server is reachable without interruptions.
• Use Wireshark to find out if your packets are "healthy". I have seen NIC-Drivers completely messing up packets.