Nicolas, although I have both options “on”, I’m one of the users affected by the problem of unwanted virtual copies.
As far as I remember, DxO creates virtual copies if I modify image+sidecar pairs on another computer and copy them back to a local disk. It does not happen if I’m working on a external disk or a network share.
I don’t understand what the DxO developers had in mind when inventing this logic, maybe you can explain the reason behind.
Therefore, I delete the database always when transferring image+sidecar pairs (as John-M dioes). The sidecars are my primary place to store the information.
Instead of brutally deleting the database, I would prefer an additional switch in DxO not to create virtual copies if the sidecar is changed externally, or a dialog asking the user if external modifications are detected.
There are other problems with the sidecars I already described in
Please consider also backup or version control scenarios. If DxO scrambles the sidecars at every opportunity without changing settings, this creates unneeded pseudo-differences or backups.
And keep entries in a predictable order. Since the sidecars are text, it can be very useful to compare two versions with a text compare tool to find the differences in the settings.