Q: My computer crashed. I want to be able to sync my iPod touch with my PC again. However, I am afraid of losing all my levels on Tiny Towers and other games when I start syncing. Is there a way to back up my apps and sync my old game progresses without losing any of the data?
A: When you connect your iPod touch a new computer or a new iTunes library it will ask you whether or not you want to replace the content that is already on your device with the content in your library.
You can simply click “Cancel” here to prevent this from happening and your iPod touch will remain connected to your computer without actually synchronizing any information with your library. Alternatively, if your computer has already been authorized for the same iTunes Store account that was used to purchase the apps and media content on your iPod touch, you will also see a “Transfer Purchases” option that can be used to copy this information from your iPod touch back to your iTunes library. This copies the raw applications and any purchased media content such as music and videos, but does not copy any application data; your application data is instead included in any backups made by iTunes or iCloud.
If your new computer is not already authorized for your iTunes Store account you can do this by selecting Authorize Computer from the Store menu in iTunes. You can also initiate the transfer of purchases by selecting the appropriate option from the iTunes File menu while your iPod touch is connected.
Unless you already have all of your applications in your iTunes library, you should take advantage of the “Transfer Purchases” option to copy this information over from your iPod touch. Performing a device backup to iTunes as part of this process is also highly recommended, as this will include your application data which can be restored from this backup just in case something goes wrong. See Backing up apps from an iPod touch for more information.
The key point is that as long as the applications themselves exist in your iTunes library, you can re-enable the “Sync Apps” feature without losing any of your application data as long as you ensure that the same apps are still selected for synchronization to your device.
When you first enable “Sync Apps” iTunes actually presents you with a somewhat scary warning dialog implying that iTunes is going to erase and reinstall all of your applications:
In reality what happens here, however, is that iTunes does a simple reconciliation to compare what’s already on your device with what’s selected for synchronization from your iTunes library. Anything that is already in both places is simply left alone and marked as “synced” while apps that are de-selected (or don’t exist in iTunes at all) will be removed, and any new apps that are selected will be added.
The catch here, of course, is that the apps must still be selected for synchronization to your device. If you enable the “Sync Apps” option with no apps selected, iTunes will go ahead and remove all of the apps on your device in order to match what you’ve selected (e.g. nothing).
You can go ahead and choose “Sync Apps” from the dialog box—nothing actually happens here until you click “Apply” so you can then go through the list and make sure that all of the apps that are actually ON your device are still selected in iTunes. When you click the “Apply” button, iTunes will simply go through a sync process matching up what’s already there and leaving it alone, after which the “Sync Apps” option will remain enabled.
The final result is that the apps on your device will match whatever is selected in iTunes, however no data is removed from your device in the process as long as the apps remain selected for synchronization.