iMac behaves inconsistently when waking from long periods of inactivity I have a late 2012 model iMac with OS X Mavericks installed. When I go to wake the iMac after a long period of inactivity (2 days for example) it behaves in one of two ways:


Sometimes the iMac wakes immediately, meaning the desktop shows up right away and all applications are snappy and ready to go.
Other times after waking, the desktop view is grayed out with a status bar at the bottom of the screen which takes a couple seconds to complete before un-graying the desktop. After the desktop is un-grayed, applications and other user-interactions are slow to respond, as if the computer is still "warming-up".


My Energy Saver preferences are set to put the display to sleep after 5 minutes of inactivity, then the computer to sleep after 10 minutes of inactivity.

Why this inconsistency in waking?
This would be explained if your iMac was sometimes in what Apple calls Safe Sleep and others (and Apple internally) call hibernation mode and is expected and intended by Apple to save energy.


http://support.apple.com/kb/HT1757




You should be able to disable this if needed by using pmset on the command line. Unless you are comfortable with the terminal, you might just leave things as Apple has configured since the hibernation should only engage for longer sleep periods to save more energy than if the machine was kept sleeping lightly the entire time.