PhoneView download’s data to a temporary location on your Mac's primary disk. If you are low on space, or if you're seeing an error message that there's not enough space to store incoming data, you may wish to use a different disk drive for PhoneView’s temporary storage. To do this:
1) Quit PhoneView.
2) Open PhoneView while holding down the option (or alt) key on your keyboard. PhoneView will prompt you with a question. Click the button labeled “Change Temporary Storage Location”. Then pick the new location.