McLean, VA (written by Rob Pegoraro/Special for USA Today) --
Question: My Mac has plenty of memory, but in the last day it's slowed down so badly, it's like its own gears are starting to seize up.
Answer: I ran into this problem on my own iMac a couple of days after installing Apple's Mountain Lion release of OS X. A computer that had not shown prior signs of stress was taking way too long to switch from one program to another, with frequent pauses while its cursor turned into the dreaded "spinning beachball of death."
(Worse yet, this only happened after I'd written a thumbs-up review of this generally worthwhile update for another freelance client.)
I returned to a system utility I'd leaned on frequently until doubling this Mac's memory to eight gigabytes, Apple's Activity Monitor. For years, tinkering types have employed this program to see which programs and background program components - called "processes" - have gotten too greedy with a Mac's processor or memory.
(In Windows, Microsoft's Task Manager performs a similar function.)
In this case, Activity Monitor (it resides in the Utilities or Other subfolder of your Applications folder, depending on your version of OS X) revealed an unexpected foe. A process called CalendarAgent that I'd never noticed before was gobbling up 3 GB of memory and counting.
A few quick searches found confirmations of the problem on Twitter and in Apple's own tech-support forums. Solutions were not as obvious; the longtime Apple-news site Macintouch suggested deleting and then recreating network accounts in the System Preferences application, but I didn't have anybody set to log into the computer remotely.
Instead, I employed an old-school remedy: Selecting the errant CalendarAgent process in Activity Monitor and clicking the "Quit Process" button to force it to close. Then the process "respawned" itself and resumed gobbling memory until I force-quit it a second time, at which point it restarted its conquest of the computer's memory yet again.
But after several iterations of this routine, CalendarAgent somehow snapped out of it and remembered its manners. In the day since then, it hasn't used up more than 70 MB of "real," physical memory (as opposed to "virtual memory," in which the computer writes some data to a special portion of the hard drive). And if this process renews its evil ways, at least I won't need a refresher course in how to attack the problem.
You shouldn't either. If your Mac might as well be marching through wet concrete, fire up Activity Monitor, and click that app's "Real Memory" and ''% CPU" headings to see which software has taxed its memory and processor most heavily. Not all of these processes are safe to "kill," but you can often free up a decent chunk of memory by force-quitting Apple's Safari browser (which has a history of memory leaks) or its Adobe Flash plug-in.
Apple's Mac App Store, unlike its App Store on the iPhone and iPad, remains optional. You can download a program from there, but with few exceptions you can also grab it from the developer's own site. How to choose?
Convenience often argues for the Mac App Store: Your downloads, purchased or free, automatically get tucked into your Applications folder, and their updates require only one click in the store app to install. In Mountain Lion, App Store programs can also display updates through that operating system's Notifications feature.
But some developers have ditched the Mac App Store because of "sandboxing" restrictions Apple imposes on software distributed through that medium - limits that can demand non-trivial surgery to a program. Others have mentioned to me that while Apple takes 30 percent of an app's purchase price, they can keep more of that revenue on other storefronts.
I don't see an automatic answer here. So if you're on the fence, look on a program developer's site or blog to see if its authors express a preference either way. Or e-mail or tweet them to ask; if they respond promptly, that's a good argument for using their software, whatever store you procure it from.