I have one Mac that mounts my image directory over the network from another Mac. If I unmount the share before I start PL (PL3 right now, the latest version I have installed so far) then the database doesn’t seem to be affected: if I poke around in various tables (after quiting PL again some time later; nothing too scientific) then I still see traces of all of my images.
For example, I can run something like the following and see just as many images as on the host that’s exporting the share:
sqlite3 $HOME/Library/DxO\ PhotoLab\ v3/DOPDatabaseV3.dopdata 'select zname from zdopitem'
My Library directory is local on each computer; it’s only the images that are on the share.
Whether or not PL has some timer on this and will eventually clean out the db I don’t know (haven’t looked that closely) but it’s not something that happens quickly at least.
Whether or not it’s the same on Windows I also don’t know, but the database implementation seems to be completely different on Windows (at least the tables are different), and there seem to be enough other Windows/Mac differences that I wonder how much code the two versions really share. Things like different SQL tables, different workspace description files, supposed dependence on macOS Mojave for a macOS api used for DeepPRIME on Mac, and feature differences, all point at much not being common.