The Special Administration Console Helper (sacsvr) service provides the ability to perform remote management tasks on a computer that is running Windows Server 2008 R2, if the computer's functions are halted due to a Stop error message. The Windows Emergency Management Services component supports two out-of-band console interfaces: the Special Administration Console (SAC) and !SAC, which offers a subset of SAC commands for use when the server has been halted.
The SAC and !SAC components accept input and send output through the out-of-band port. SAC is a separate entity from !SAC and the command-line environments in Windows Server 2008 R2. After a specific failure point is reached, Emergency Management Services components determine when to shift from SAC to !SAC. !SAC becomes available automatically if SAC fails to load or does not function.
The Special Administration Console Helper service allows you to create inbound communication channels through the Command Prompt window. If the Special Administration Console Helper service stops, SAC services are not available.
This service is installed by default in Windows Server 2008 R2, and its startup type is Manual.
When the Special Administration Console Helper service is started in its default configuration, it logs on by using the Local System account.