The Restart Manager API can eliminate or reduce the number of system restarts that are required to complete an installation or update.
The Restart Manager API can eliminate or reduce the number of system restarts that are required to complete an installation or update. The primary reason software updates require a system restart during an installation or update is that some of the files that are being updated are currently being used by a running application or service. The Restart Manager enables all but the critical system services to be shut down and restarted. This frees files that are in use and allows installation operations to complete.
For more information: https://msdn.microsoft.com/en-us/library/windows/desktop/cc948910