Hi Jim, thanks for your question. younity can access files on a machine that is sleeping, assuming it is not the type of "hard sleep" that results from you going to your Apple icon (upper left) and selecting "Sleep". If it auto-sleeps, younity will itself make sure your Mac is available via the Wake on LAN features built into modern operating systems and not allowing the computer or hard disk to be put into a hard sleep mode. (As an FYI, these features are controlled in your "Energy Saver" setting within System Preferences.) Hope that helps answer your question. Let us know if you see any behavior that suggests otherwise. Thanks.