Sorry for not being more precise
DL discs are the so-called Dual Layer discs, i.e. DVD containing two overlapped layers that can be burned with data. Most of DVD video nowadays are DL discs.
If you want create a 1:1 copy (i.e. a perfectly identical copy) of a data disc, then the best option is to make a copy of the original disc is to use a software like ImgBurn in “Read mode”, save an ISO file in HDD, and then burn the ISO file on a blank disc again with ImgBurn.
You can use also DVD Shrink to create the ISO, but for DL discs the best option is ImgBurn.
DVD Shrink is the best option only if you need to remove some unwanted contents from the original disc before to burn on a blank disc.