Here are some tips for syncing databases for the FIRST TIME via Dropbox (so you don’t spend countless, hopeless, wasted hours resending DevonThink databases that failed to properly synch on the first upload).
These are important because the DevonThink \ Dropbox combo is VERY finicky. You must send an absolutely pristine database on your first synch: No broken links, no missing files, no zero byte files. Moreover, even for the most gargantuan database, the initial upload must take place perfectly in its entirety. Even the tiniest error at the very last byte will cause the whole thing to be rejected and you will have to 1) trace down the error, and 2) start the entire synch over again.
Sooooooo, here are 5 tips that could save you hours – perhaps days – of fruitless repetitive uploads.
Tip 1. Synch a SMALL database as your first with Dropbox. Get a quick success to establish the Dropbox-DevonThink link. Then, after that first successful synch, as the official DevonThink help video (more a commercial IMHO) implies, immediately uncheck the DevonThink app from your local machine(s) Dropbox account:
Dropbox | Preferences | Advanced | Selective Sync | Change Settings...
You do NOT have to upload all your databases before unchecking that link. In fact, the sooner the better – immediately after your first database has successfully synched to Dropbox (a point which should have been made clearer in the video, I think).
Tip 2. If you are synching a database that includes INDEXED files, save yourself potential hours of heartache! BEFORE attempting a synch of such a database, update your file indexes. “Missing files” will cause a database to be rejected. You will have to remove missing files and start the entire synch over again. To avoid this unfortunate time sink, see the next tip.
Tip 3. Select the database you intend to synch. Under the Tools menu, select: Verify and Repair. (Even if you don’t suspect any problems, this gives DevonThink an opportunity to unearth hidden problems lurking in the shadowy depths that you had no idea might be there.)
Tip 4. If ANY errors are returned from the Verify and Repair routine, go back to the tools menu, and select Rebuild Database. Whatever time that takes is NOTHING compared to having to send your database multiple times to the Dropbox server only to have it rejected mid-stream for some ittty-bitty inconsistency that you could not otherwise know was there. And, of course, this likely will happen ~9.75 hours into a 10 hour upload. 
Tip 5. Select all files. Click the SIZE column to order files from smallest to largest. Delete or reconfigure into a larger file any ZERO-byte sized files. These tend to make Dropbox choke and then reject your attempt to upload your database for synchronization.
…….
Bonus Tips for Synching In General
Bonus tip 1: Make sure you store your DevonThink databases OUTSIDE Dropbox and only use Dropbox for the auto-synchronizing. Housing DevonThink database files in Dropbox folders on your Mac invites emergencies, nightmares, and disasters.
Bonus tip 2: You will need space on Dropbox for your DevonThink files there. If you are close on space allocation, delete files from Dropbox a few days before you’ll need it! Reason: Dropbox ‘protects’ you from accidental deletions by retaining files in a cache folder (see below) for about three days so that you can Undelete and restore files. Meantime, your free space on your Dropbox account may not reflect the recent deletions. There is a workaround that MAY help IF you you delete the files in the Dropbox cache on ALL the computers that were linked to the files and folders you just deleted.
The Dropbox cache can be found at:
~/Dropbox/.dropbox.cache
[b]Note[/b]: Dropbox may DOWNLOAD copies of these deleted files and place them into this cache on your local Mac(s) to make sure that you have them (even if you don't want or need them)! In my case, I moved thousands of image files from my Dropbox folder to a remote hard drive, and then deleted the folder on the Dropbox web site. Dropbox then proceeded to download tens of thousands of (deleted) image files to this cache folder, which I then had to delete on multiple machines. Ugh.
Bonus tip 3: To keep an eye on the progress of your synch (you do watch the water boil, yes?), click Window | Activity and Window | Log. Activity should hum along steadily during a synch. The Log should be blank, unless there’s a problem. In that case, you will want to take note of the cratering cause and respond accordingly.
Bonus tip 4: There is nothing obvious about it, but after you sync your DevonThink database on Mac A, to access that database on Mac B, you IMPORT it via the Preferences dialog. The entire database downloads one record at a time and then “completes” the sync procedure (a process of moving files and “committing” the database) so it can take as long as the initial upload! Once you have the synched database downloaded to the additional Mac(s) store it locally outside your Dropbox folder, such as in your Mac’s Documents.
Bonus tip 5: Sync your database and CLOSE it when you are finished with it on a given Mac. Keeping the file open is inviting Sync Errors.
If you follow these procedures, based on my beleaguered, battle-scarred experience, you will have a much smoother – and much faster – synchronizing experience with the DevonThink databases that you value and want to keep in sync across multiple Macs.
(Does your experience vary from mine? I’d love to benefit from what you have learned…)
Cheers,
Don
and the database has a bad bit of data. To this end, it is a good habit to run an occasional Tools > Verify & Repair (though I prefer the hamfisted Rebuild myself).