The back up process can be a pain for iPhone users who have a lot of applications installed on their device.

If you’re impatient (or bored of the backup process) to synchronize only your iPhone and try to cancel the backup, the iPhone won’t sync, since it makes the backup before it synchronizes your datas. Worst, according to a blogger:

The other problem is that if you ever cancel a backup (by clicking the ‘x’ next to the progress bar), it apparently corrupts the existing backup — so if you do then go to restore your iPhone, the backup won’t be usable.

The solution is a command line to type from the Terminal; it will prevent your iPhone from backing up the datas and directly sync.
Prior to do this be sure iTunes is closed.

defaults write com.apple.itunes DeviceBackupsDisabled -bool YES

To revert the change you made and make iTunes backup again your iPhone again, just type this from Terminal:

defaults write com.apple.itunes DeviceBackupsDisabled -bool NO

Backups are very important since they do create a copy of your SMS, notes and application-specific data. As a result, if you ever have to restore your iPhone, all these valuable data will be back to your iPhone from the latest backup you’ve made.

Posted in Macintosh Tips & Help, iPhone & iPhone 3G