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10.9: Disable App Nap System Wide System 10.9
The Finder/Get Info checkmark for preventing App Nap sometimes disappears, seemingly at random. Maybe the app updates itself, or just writes something to the application directory and the checkmark is gone. The next day your overnight render is at 10%. So in Terminal, type:
defaults write NSGlobalDomain NSAppSleepDisabled -bool YES
This seems to prevent App Nap completely, looking at the Activity Monitor » Energy » App Nap column. Running programs need to be restarted for the change to take effect.

[crarko adds: I tried the command; not sure if it's really made a difference. I don't do overnight renders, but if people who do leave lengthy processes going care to comment, we care to listen. I'm really curious about the check box resetting itself.]
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10.9: Disable App Nap System Wide
Authored by: Manyk on May 09, '14 02:27:11PM

Entered command in Terminal, and did fresh boot of OS X. So far none of my apps are taking naps!

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10.9: Disable App Nap System Wide
Authored by: simsamsep on May 10, '14 04:37:18AM

Does the App Nap feature only exist on specific hardware? On my mid-2007 iMac with OSX 10.9.2, I can find no applications that have the "Prevent App Nap" checkbox under General in Finder Info, also none of Apple's applications have it. Only the "Locked" checkbox is there.

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10.9: Disable App Nap System Wide
Authored by: benwiggy on May 11, '14 09:53:16AM

App Nap is supposed to only kick in:
if an application's windows are completely hidden (either actual hidden or behind another foreground app);
if it's not doing something significant, like playing audio.

So I'm not sure why it should throttle a pro app doing rendering overnight.

App Nap seems to get blamed for all sorts of things, so it's worth stating that most users don't need to turn this off.

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10.9: Disable App Nap System Wide
Authored by: ambrose on May 13, '14 04:46:27PM
The Apple Developer Documentation on App Nap explains it this way:
An app is considered to be a candidate for sleep if:
  • It is not visible—if all of an app’s windows are either hidden by other windows or minimized in a hidden dock, and the app is not in the foreground
  • It is not audible
  • It has not explicitly disabled automatic termination
  • It has not taken any power management assertions

  • When all of these conditions are met [...] the app is placed on a scheduling queue that rarely gets actual time on the CPU. The app wakes up automatically when the user brings the app to the foreground or when the app receives a Mach message or Apple event.
    The documentation goes on to describe the coding the developer needs to employ to opt out of having his application be subject to App Nap's invocation, adding
    Note: If you experience problems with App Nap, you can temporarily disable it for a particular process by typing:
    defaults write NSAppSleepDisabled -bool YES

    That's arguably a superior method to disabling App Nap system-wide, as it seems just as resistant to the "disappearing checkbox" syndrome. (By "temporarily," the documentation means the change does not survive a restart.)

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