Sql-server – Why did SQL Server go into single user mode


I've had an application that's been running great for several months. Thankfully I use try/catch blocks in my database calls because this morning I get an email alert from my catch block that said,

Message: Login failed for user 'NT
Server is in single user mode. Only
one administrator can connect at this

Source: .Net SqlClient Data Provider


So I go and try to access the application, and yep, verified that it doesn't work.

I was able to remote desktop over to the server and log into SQL Server which suddenly "fixed" the issue, but I don't know why this happened. ("Fixed" as in now the application does it's normal CRUD operations.)

Does anyone know why this might have spontaneously happened?

Also, if I go to database -> properties -> options -> State, I verified that Restrict Access is in "MULTI_USER".

The app is powered by the mighty SQL Server 2005 express. Is that the problem?

Best Solution

Did you check your Windows Event Logs to see if anything happened to the server? Did it reboot after installing any updates?