Understanding Offline File Sync

When a user chooses to make a particular file available for offline use, Windows automatically creates a copy of that file within the local cache on the user's local computer. When the network becomes unavailable (for example, when a mobile user disconnects from the network), the user can then work with the local copy of the file by opening it and editing it using the appropriate application. Later, when the network becomes available again (for example, when the mobile user reconnects to the network), Windows will synchronize (sync) the local and remote copies of the file. In addition, users can also manually sync their locally cached versions of files with the remote copies whenever they choose.

When a file that has been made available for offline use is modified, the local and remote copies become different. What happens now when a sync operation occurs depends on which copy of the file has been modified:

• If the local copy of the file stored in the local cache on the user's computer has been modified but the remote copy is unchanged, the sync operation typically will overwrite the remote copy with the local version because the local copy is the more recent version of the file.
• If the local copy is unchanged but the remote copy has been modified, the sync operation typically will overwrite the local copy with the remote version because the remote copy is the more recent version of the file.
• If both the local and remote copies of the file have been modified, a sync conflict will occur and Windows will prompt the user to resolve the conflict in one of three ways:
  • By deciding which copy (local or remote) of the file should be considered the master copy and which copy should be updated
  • By deciding to keep both copies of the file as is, in which case one copy of the file is renamed and both versions are then copied and stored in both locations (local and remote)
  • By ignoring the conflict, in which case the conflict will usually occur again the next time you try to sync the file

Sync operations also have an effect when offline files are added or deleted. For example, when the local copy of a file is deleted, the remote copy will also be deleted during the next sync operation. And when a file is added to one location (local or remote) but not the other, it will be copied to the other location when sync next occurs.