I’m using the same photo library, stored on a big USB 3.1 external SSD drive on two different computers, depending if I’m at home or roaming around.
I use projects quite a lot, to keep in the same place sets of picture that I can finalize when I have time or am in the mood. However, when moving from one computer to another, I loose the project assignment.
If the assignment could be copied to the dop file in addition to the database content, the second computer could sync these after a simple rescan. In addition, if you reinstall your computer, or move to another one, or corrupt your database, or move your photos to a bigger drive, these assignements could be recovered after scanning the right folders.
I vote for too.
But that has already been said, but everything related to the addition/deletion/modification of the image must be in the DOP, so as to find everything in the event of a problem on the database.
Because the image locations in the database are keyed to the serial number of the hard disk. So if you restore that database and images to another disk after a disk failure, the database doesn’t recognize the location of your images because the serial numbers don’t match and all edits, keywords, project associations are lost. It an absolutely abhorrent design that, in the absence of a disk in a system with the same serial number, the program can’t do a basic tree search to find the images and relink them. Edits and keywords can be re-imported from the DOP sidecars but the project settings cannot.
So you’re screwed with respect to projects.
All the gory details are here (note this was for a change in the low level structure of an existing disk but a replacement disk would suffer the same fate, even if you used a cloning utility to make the copy.)
Indeed … and the more I think about it the more baffled I am with this design. I cannot understand why they do it this way. I logged a ticked and exchanged emails with their support urging them to look into this as it needs a fix.
BTW - I’m voting for projects to be put in the DOP file … that will help. Never use PL without DOPs set on as default … you will lose your edits if your hard disk blows up without them …
Yes it’s really inexcusable. With this architecture sidecars shouldn’t be optional. I know some people don’t want to deal with them and I understand. But if they realized regardless of any backup strategy that all of their edits for all time are at risk without sidecars o think they would feel differently.
Unfortunately most people won’t know until they suffer like the guy in the linked post did. He was able to recover his edits but it took low level knowledge of computer systems and scary tools that most photographers shouldn’t be using.
. 
and yes a bit of IT knowledge was essential … and a bit of luck.