That just refreshes the METADATA.OPF in the title folder. That is a backup of the DATA you see,
just in case the DB gets damaged,
You need to back up your Library someplace OFF the computer / hard drive to save your books with their metadata.
Export/Import on the Library Icon
can do this, but it always does a FULL, which can be time/space consuming. IMHO do that whenever you make changes or install new Plugins (those are in the config folder)
Use a file sync program to incrementally update a separate Library copy.
Freefilesync seems to do a fantastic job.
Always STOP Calibre to do a Mirror (1 way) sync
Don't have sync active while Calibre is running.. avoid 2 way sync. it fights changes
