SQL Server Management Studio, only one person can login on it.
By default it only accepts local connections. To change it to accept remote

connections use:

sp_configure ‘remote admin connections’, 1;
GO
RECONFIGURE;
GO

Using a DAC
Open Management studio, and open a new Query connection to admin:instance using a

sys admin account. You cannot use the Object Explorer with DAC. If you just open an

try to connect to the server you end up with this error:

Dedicated administrator connections are not supported. (ObjectExplorer)

You need to open the management console then cancel the connect to server window

and select a new querry and go admin:servername\instance

Here you can execute querries like

select Session_id, login_time, cpu_time, memory_usage, reads, writes, login_name

from sys.dm_exec_sessions WITH (NOLOCK)