Microsoft SQL Server 2012 provides a dedicated administrator connection (DAC). The DAC lets an administrator access a running server to be able to execute diagnostic functions or T-SQL statements, or troubleshoot problems on the server, even when the server is locked or running in an abnormal state and not responding to any other type of user connection. By default, the DAC is available only from a client on the server. But if you set the
Remote Admin connections option to
1, the DAC is available from a remote connection as well. By default, the DAC listens only on the loopback IP address (127.0.0.1), port 1434.
The following is an example of this option: