SQL Server provides a dedicated administrator connection (DAC). The DAC lets an administrator access a running server to execute diagnostic functions or Transact-SQL statements, or to troubleshoot problems on the server, even when the server is locked or running in an abnormal state and not responding to a SQL Server Database Engine connection. By default, the DAC is only available from a client on the server. To enable client applications on remote computers to use the DAC, use the remote admin connections option of sp_configure.
By default, the DAC only listens on the loop-back IP address (127.0.0.1), port 1434. If TCP port 1434 is not available, a TCP port is dynamically assigned when the Database Engine starts up. When more than one instance of SQL Server is installed on a computer, check the error log for the TCP port number.
The following table lists the possible values for the remote admin connections option.
|0||Indicates only local connections are allowed by using the DAC.|
|1||Indicates remote connections are allowed by using the DAC.|
The following example enables the DAC from a remote computer.
sp_configure 'remote admin connections', 1; GO RECONFIGURE; GO