The Science of Syncing

[wildonrio]

I think there are very few of us (including myself) who fully understand what exactly happens when we sync our phones. With the iPod, we could all assume that the iPod was being synced to everything on the computer. But with the iPhone, we know this can't be happening with contacts, bookmarks, etc or all your new contacts and bookmarks from the day would be erased every time you synced your phone. But as far as pictures, we are constantly adding new pictures from the computer and also from the iPhone, so there must be some type of merging that also happens. This is what I THINK is happening when we sync our phones:

The computer is syncing to the iPhone:
-New music
-New videos

The iPhone is syncing to the computer:
-New contacts
-New settings
-New texts
-New bookmarks

The computer and iPhone are merging:
-New pictures

Am I missing anything? I will update this post as people explain this better to me...

 

[Beau]

we know this can't be happening with contacts, bookmarks, etc or all your new contacts and bookmarks from the day would be erased every time you synced your phone.

You're thinking is an all or nothing affair... iTunes does a snapshot sync with playlists because it makes sense - playlists represent what you actually want on the device. But everything else, nope. Once the devices have been properly synced from the beginning, it's additive (or subtractive) from that point on, and merging takes place for same records.

No need to scratch your head over this - use cases are easy to concoct to figure this out.

For instance for contacts - add a contact on your phone. Add a contact in Outlook. Sync. Both entries now exist on the computer as well as the device. For same record editing a merge is done, and when there is a collision iTunes will alert you to resolve. Take a contact on your PC, add an email address. Take the same contact on the device, add another email address. Sync. Both devices now have both email addresses. Now change the phone number for that entry on your PC to something, change it on the device to something else. Sync. Notice the popup.

 

[wildonrio]

You're thinking is an all or nothing affair... iTunes does a snapshot sync with playlists because it makes sense - playlists represent what you actually want on the device. But everything else, nope. Once the devices have been properly synced from the beginning, it's additive (or subtractive) from that point on, and merging takes place for same records.

No need to scratch your head over this - use cases are easy to concoct to figure this out.

For instance for contacts - add a contact on your phone. Add a contact in Outlook. Sync. Both entries now exist on the computer as well as the device. For same record editing a merge is done, and when there is a collision iTunes will alert you to resolve. Take a contact on your PC, add an email address. Take the same contact on the device, add another email address. Sync. Both devices now have both email addresses. Now change the phone number for that entry on your PC to something, change it on the device to something else. Sync. Notice the popup.

It doesn't always do merging does it? Like say if I delete a song out of my library that had previously been synced to my iPhone and then I try and sync again, it will just delete the song right off my iPhone without prompting me.

 

[Beau]

Because that's how a playlist is supposed to work. It is a snapshot of what is supposed to be on your phone. Think of it like a contract. Or a list of specifications.

Everything else - settings/notes/calendar items, do not abide by this. They are just stuff you do to either device.

 

[pubcrawler13]

So here's a question (I'm at work at the moment and can't try it out for myself)... say, for example, I've got contact A and contact B on my phone, and the same two contacts in my PC address book. If I remove contact A from my phone then sync, will it remove contact A from my PC address book or re-add it to my phone?

 

[Tinman]

Because that's how a playlist is supposed to work. It is a snapshot of what is supposed to be on your phone. Think of it like a contract. Or a list of specifications.

Everything else - settings/notes/calendar items, do not abide by this. They are just stuff you do to either device.

Notes do not sync, though I wish they did. Not sure what you meant by settings, but if you meant settings as in iPhone settings they seem to be backed up, not synced.

Photos sync one-way and it doesn't appear any data is sent back from the iPhone regarding the Photos app.

Bookmarks, contacts, and calendar sync both ways. iTunes syncs music one-way, but collects/sends player data to/from the iPhone. Video is sent to the iPhone one-way, but is deletable on the iPhone and this info is then sent back to iTunes (i.e., if you delete it off the iPhone it won't be resent by iTunes).

Although I have bought and configured iPods for others in the past, I never actually owned one. So I am really liking the iTunes syncing with regards to music, video, and podcasts. Listen to the first half of a podcast on my computer and it picks up where I left off on the iPhone. Love it.



--
Mike

 

[Tinman]

So here's a question (I'm at work at the moment and can't try it out for myself)... say, for example, I've got contact A and contact B on my phone, and the same two contacts in my PC address book. If I remove contact A from my phone then sync, will it remove contact A from my PC address book or re-add it to my phone?

It will delete it from the PC address book (at least it should--and that's the way it works with my iPhone when syncing to Outlook).


--
Mike

 

[pubcrawler13]

It will delete it from the PC address book (at least it should--and that's the way it works with my iPhone when syncing to Outlook).


--
Mike

Gotcha - so if I'm understanding correctly, the syncing process gives priority to the contents of the phone over the contents of the PC. Thanks, that's good to know!

 

[Tinman]

Gotcha - so if I'm understanding correctly, the syncing process gives priority to the contents of the phone over the contents of the PC. Thanks, that's good to know!

It's not actually giving priority to either the PC or the iPhone: they both get equal billing (for Contacts).

If, using your previous example, you instead deleted contact A on the PC it would get deleted from the iPhone during the next sync.

Essentially you should be able to edit anything, anywhere, and it should sync. When there is a conflict, say by changing the same piece of data on both the PC and the iPhone between syncs, you will be presented with a conflict resolver message in iTunes (as previously mentioned):

If you choose to review now you will be taken to a screen showing both records, allowing you to choose which one to keep:

To me the iTunes/iPhone syncing combo is pretty darn good. It does field-level syncing, as opposed to record level. This means you only get a conflict if you change the same field in the same exact record on both the PC and the iPhone. In the above example had I not changed the same phone number in both Outlook and on my iPhone no conflict resolution would have been required.

The syncing provided by my Palm Treo to Outlook is only at the record level: if I change two different fields in the same contact, on both the PC and Treo, Hotsync throws up an error log that it has now duplicated both contacts. Ugh.


--
Mike

 

[pubcrawler13]

Thanks for the info Mike - that helps a lot!
Cheers,
Andy