General help

Hi,

I wonder which data is actually stored in mdl_log and mdl_backup_log. I know most of the data is like which resource was used by which student at which time. But is any quiz related data stored in these two tables?  80% of the data which is stored in my database belongs to these two tables. I would like to delete the data and change my backup settings, so that much less logs are saved. But I don't won't to lose any quiz results and or other important data. http://docs.moodle.org/en/Logs isn't very helpfull when it comes to the details about which data is stored.