Surface Area Configuration for Features (DAC) - Database Engine
The dedicated administrator connection (DAC) allows an administrator to connect to a server to execute diagnostic functions or Transact-SQL statements. The DAC can be used when the Database Engine will not respond to regular connections. By default, this feature is only enabled for a local connection. Enable this option to use the DAC from a remote computer. On cluster configurations, you must enable this option to connect with the DAC.