by Eloy Lafuente (stronk7).
Hi,
AFAIK, it looks for both log entries (not being "read" operations) and also for the course->timemodified database field.
If BOTH checks don't reveal any change since the date of the previous backup... then the course is skipped. (by default no courses are skipped, only those fulfilling the 2 conditions above are).
Ciao