Solution for “Server is in single user mode. Only one administrator can connect at this time.”

I ran into the error message in the title today, while trying to access a database on my local machine after upgrading various stuff. Among other things, I had installed the newest version of Microsoft SQL Server, and now I could not access my DB. Here’s how I fixed it.

It took me a little while, but I eventually found the cause: For some reason an -mhad been added to the list of parameters used when starting up the service that runs the database server. If you’re in the same situation, you’ll find this in the application Sql Server Configuration Manager.

Right click SQL Server (MSSQLSERVER) and select the tab Startup Parameters:

Click to select and remove the parameter “-m”

I don’t know why the -m parameter was there to begin with – perhaps I’d configured it that way unwittingly during the installation.

In any case, selecting and removing it and restarting the service MSSQLSERVER fixed my problem, and let me access my database again.

PS: Still not working? Look for an -f

A few other posts I read indicate that an -f parameter can have the same effect, so you might want to look for that if the above doesn’t fix your problem.

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