Anything Technology

After upgrading compatible iDevices to iOS 5, many have been asking what it exactly means when an app is “cleaning…” itself. If you don’t know what it looks like, here is a screenshot of my iPad that I took today: 

Simply put, iOS 5 is clearing the contents of the Caches and tmp directory. Every iOS app has its own home directory where it stores files. Every file that an app puts there gets backed up when you sync your device, with the exception of anything inside the Caches and tmp directory. With iCloud backup in mind, Apple designed iOS 5 to keep an eye on apps that store too many files in any backed-up directory and to delete any non-crucial, non-user-generated files that may have found its way into the said home directory.

Many developers have recently received emails from Apple like this:

In recent testing it appears that [your app] stores a fair amount of data in its Documents folder.

Since iCloud backups are performed daily over Wi-Fi for each user’s iOS device, it’s important to ensure the best possible user experience by minimizing the amount of data being stored by your app.

In addition to purchased music, apps, books, Camera roll, and device settings, everything in your app’s home directory, including its Documents folder, is backed up to iCloud.

Data stored in the application bundle itself, the caches directory, and the temp directory is not backed up to iCloud. Your app should store data in these locations according to the iCloud Data Storage Guidelines on <http://developer.apple.com/icloud/documentation/data-storage/>.

Please review these guidelines, make any required changes to your app, and submit an update to the App Store.

While this originally posed serious problems for apps that relied on their home directories to provide contents offline (that is, contents saved for offline viewing getting deleted by iOS), many have already issued updates to resolve this problem.

“Cleaning…” simply means that your iOS 5 device is clearing out temporary files to recover storage space from greedy and/or poorly designed apps, and really is nothing to worry about in terms of your iOS device working as it should.