Restoring OneNote data from the local cache (08 Oct 2017)

This is how it all started: After withstanding the constant nagging for a while, I finally gave in to those prompts to upgrade to Office 2016 on my developer laptop. During the upgrade, OneNote 2016 warned me that it may lose those few notes which had not been synced to the cloud yet. This is because OneNote 2016 creates a new empty local cache during installation, which will then fill incrementally by downloading notes from the cloud.

I shrugged off the warning because I was quite certain I had not made any significant changes recently, so everything should have been synced already. Of course I was totally wrong.

After installation, OneNote 2016 would not display about two months of notes even though I had taken them in OneNote 2013 on the very system on which I performed the upgrade. It turned out that OneNote had indeed not synced any of those notes to the cloud, i.e. it had not synced properly for two months or so.

The bad news is that I will probably never find out why and how synchronisation failed for such a long time, and why I never noticed any warnings about it.

The good news is that I managed to restore my notes. OneNote 2016 had created a new local cache below %LOCALAPPDATA%\Microsoft\OneNote\16.0, but it had not deleted the old OneNote 2013 cache below %LOCALAPPDATA%\Microsoft\OneNote\15.0, and this saved my bacon.

Others have fallen into the same or similar traps before, of course, and so there are a number of related discussions out there on the topic, for example at https://answers.microsoft.com/en-us/msoffice/forum/msoffice_onenote-mso_other-mso_2010/recover-information-from/8bf30713-316b-49cb-abc3-a8ce8e4b310d. A number of approaches are mentioned, such as:

• Restore OneNote sections from the C:\Users\<name>\AppData\Local\Microsoft\OneNote\15.0\Backup directory
  • This worked only partially because the latest backup was already several days old.
• Extract notes from the old OneNoteOfflineCache.onecache file in C:\Users\<name>\AppData\Local\Microsoft\OneNote\15.0\ by running onenote.exe /forcerepair on it.
  • This would fail because both OneNote 2013 and OneNote 2016 would complain that the cache file was of a format written by a "future version" of OneNote. (Which wasn't true, because the local cache file was written by OneNote 2013.
  • See also https://support.microsoft.com/en-us/help/825779/how-to-recover-information-in-a-damaged-onenote-section-file

The approach which did work in the end was as follows:

• I installed OneNote 2013 on a separate Windows VM.
• Then I copied over the cache files from my developer laptop to the Windows VM, i.e. both the OneNoteOfflineCache.onecache file and the OneNoteOfflineCache_Files directory (which holds all the attachments), overwriting the default local cache files of the OneNote 2013 installation on the VM.
• After starting OneNote 2013 on the VM, it displayed all notes just fine. Big sigh of relief.
• Syncing those notes from the VM to the cloud would not work, though. I first had to move all the notes to a new section in the affected notebook, and then wait until all notes had been synced.
• And now, finally, the notes reappeared in my OneNote 2016 installation on my developer laptop as well.

I also could have uninstalled OneNote 2016 on my developer laptop and replaced it with the older OneNote 2013, and in fact I tried, but the OneNote 2013 installer told me to uninstall all of Office 2016 first, from which I shied away.