System goes to sleep while programs are running (does not sense activity)

I know it's not a permanent solution but as a workaround you can use Caffeine to prevent sleeping. It's available free at the Mac App Store.

Same problem here too. Started after installing ML.

I have the same problem. My system goes to sleep while converting video files, streaming videos to my TV etc. It also stops downloading in sleep mode. Very annoying.

Today an upgrade for Unison was available from the app store, it said it fixed dropping connections under 10.8. (Unison can be used to download very large binary files) Installed the update, and as promised it no longer stops downloading in sleep mode. So I'm not sure anymore if this is a bug in ML. Maybe ALL apps need to be updated to take "advantage" of the new power management system in ML. I hope not, but it sure looks like it.

According to Ars Technica:

"In Mountain Lion, OS X no longer pays attention to disk activity when deciding if it's OK to put the system to sleep. Instead, Apple recommends that applications make what Apple calls "power assertions" as a way to tell the OS when they're doing some useful work that the system should stay awake for. This policy allows the OS to put the system to sleep the moment there are no applications still holding power assertions to prevent the action."

Apparently the "caffeinate" terminal command can be used in conjunction with specific processs to keep your machine awake until the process completes but it also seems that apps will have to be updated to comply with this new power management protocol. I've noticed the problem with Retrospect 9, HandBrake and RipIt so far...

I have not figured out the terminal commands for using caffeinate with these apps—if anyone has some pointers I would be grateful.

Thx

Yup you could use caffeinate or just open up a file in Quicktime. Just by having Quicktime open it will prevent the system from sleeping which you can verify by typing following command in terminal:

pmset -g assertions

Seems that Apple has gotten pretty aggresive with power managment and apps will have to be updated to deal with it.

The new power management sounds like a good idea for a laptop. But on a desktop I don't really see the point. Most people will adjust their energy settings, set it to never sleep and end up using more power than before. Adding an option to the energy saver letting you choose what type of computer you're using would have been a better and "greener" choice. At least for now.

Yes - I agree. It is the Apps that know best whether to allow the sleep timer to be over-ridden or not. But we seem to need to get more developers to realise this.

It affects servers too. My own campaign is to get Logitech to fix the Squeezebox server for the Mac so it prevents sleep while actively serving a Squeezebox music player.

I, for one, am delighted that my Mini now sleeps reliably according to the preference settings. Caffeinate is fine as a workaround for Apps until developers fix them, but it is not any use to the end user for servers like the Logitech Media Server.

Interesting that they have made these changes that have caused me such mishaps. Funny that apple's aperture 3 software doesn't send the requisite power management requests, as i woke up this morning to find a slideshow export that should have run all night and been completed was asleep as 23%! If they cannot update their own sofware to work under ML without mishap how practical or likely is it that all thir parfties will be able to do so.

Even worse, not even Apple's OS level software has been adapted, disk utiilty from Mavericks' installer package still goes to sleep while doing a large backup ("crate new disk image from disk"), forcing the user to stay in front of the computer and creating some keyboard or mouse/trackpad activity from time to time.

I found this thread investigating the same irritating bug, I mean, new Apple design choice. Now I have to sit in front of the Mac to ensure a 50GB data burn completes without losing discs, data or time. Annoying.

Imran

go to terminal an type "pmset noidle", this will prevent sleep until you close it.

Try to build a large cross-platform application, 'sage' OSX on Maverix 10.9.5. Using the information from evmans I thought I could issue the following:

pmset noidle&

make

killall pmset

But alas this sleepy operating system sleeps anyway. So it seems that the pmset command needs to sit there in it's own terminal window.