"File not yet available" and apparent file loss

So what’s the “best” or at least recommended way of doing syncing if not via the CloudKit built into the app? Using just a plain iCloud folder? A DropBox folder? WebDAV on a NAS?

There is no best option. It depends on the environment and the actual needs.

Also, sync is one of the most thoroughly documented aspects of the DEVONthink suite.

The first question you need to ask yourself is, “Do I need a remote sync option?”. Consider these questions…

  • Do you have a colleague, assistant, significant other, etc. that needs frequent updates to synced data?
  • Are you using a shallow sync, i.e., Download Files: On demand in DEVONthink To Go? Otherwise, a local sync is the advocated approach.

If the answer is no to either question, a local sync on your network is suggested.

We have information available in a variety of places…

FAQ

There is a Sync section on our Questions and Answers page.

On our forums:

There is a forum post on syncing: Sync Types Explained. This is a good place to start.
There is also one specifically about Bonjour: Bonjour Simplified

Help and Manuals

Sync is covered in the Help for each application:

  • For DEVONthink, sync is covered in the Help > Documentation > In & Out > Sync, Preferences > Sync, and Troubleshooting > Sync Issues.
  • For DEVONthink To Go, sync is covered in the ? > Help > Sync your databases section.

Manuals can be downloaded here: Manuals

Support Assistant Tutorials

There are tutorials in DEVONthink’s ​Help > Tutorials​.

I can do Bonjour from some of my devices but not others if that’s what you mean by “local syncs”.

Why’s that?

Is the recommended backup strategy simply copying the database files to an external source periodically or is there some better way?

At a bare minimum, copying the databases to an external drive would work. However, it’s not going to run on a periodic basis like an actual proper backup.

As has been discussed many times, sync is ​not ​a backup, neither advertised nor advocated as such. We strongly advocate proper primary backups using TimeMachine (or similar snapshot-style backup applications) and external drives. Also, you should read the series of articles we posted: