SQL Server->> DAC (dedicated Administrator Connection) dedicated Administrator connection

A dedicated administrator connection is a special SQL Server server diagnostic connection that is used to connect to a server for server performance or error diagnosis in a normal or standard connection form that cannot connect to a SQL Server server. The DAC also supports secure encryption and only members of the sysadmin server role group have permission to use the DAC. By default, the DAC connection is not allowed to be turned on from clients other than the server, except that the Allow remote admin connections is set by sp_configure. The DAC's listening port is 1434.

Using the DAC via SSMS

When entering the server name, add "admin:" in front of the server instance, such as Admin:servername/instance

Limit:

1) DAC is not allowed with the restore and backup statements because it does not allow multi-threaded operations

Reference:

Diagnostic Connection for Database Administrators

The dedicated Admin connection:why you want it, when do you need it, and what's the Who's Using it

SQL Server->> DAC (dedicated Administrator Connection) dedicated Administrator connection