Failed to Connect to server admin:servername\instance Error..but it does connect!

At the SQL Pass Summit last week, I attended a Pre con by Paul Randal and while using a Dedicated Admin Connection he seemed to get a strange error in Management Studio. It seemed he was familiar with the error so i thought I’d try to get to the bottom of it as it just happened to me…

The Issue

Whenever you try to open an admin (DAC) connection to an instance via SSMS, a random error pops up even though the connection is successfully made:


After you Ok the error…SSMS is still happy!..


Why does this happen?

This is all down to how the Management studio Query window is opened. IF an existing normal connection to the database already exists, then you will get the error. The key is to not have any connectivity to the server in management studio so a completely fresh connection can be opened and not a connection switch in the an existing query window!

Normally you will have object explorer open and the normal course of action is to press the ‘New Query’ button which will open a connected session using the connection context in your Object explorer. Then when you try to switch the connection, the error will happen.


To do cleanly (not that it matters!), close the object explorer or have a clean SSMS GUI and press the new query window. This will prompt for the connection where the DAC details can be entered and it will open the connection cleanly.