If you have a through ticket on DY, then you will be rebooked on the next OSL-BGO if there is a delay.
Procedure on arrival is to go through passport control (MUCH quicker than the US theater), get your luggage (appr. 20 - 30 minutes after landing), go through customs and drag your luggage upstairs to drop your luggage at recheck - reasonably quick. If you want to go native, by booze in the huge arrival tax-free: remember to get it in a sealed bag if you want to take it as cabin luggage OSL-BGO (you do!).
Is your friend travelling as well, or are you just meeting at the airport? If travelling on, I'd suggest going through security at once. The bar/food offerings in the domestic part of the terminal are just so-so, but as distances to some of the gates (19 A-F and gates below 11) are quite long, and DY boards early, I prefer to be past security ASAP (even though waits usually are short at OSL). If your friend is not travelling, there's a nice bakery in the check-in hall, as well as several fast food type places in the arrival hall. Or go over to the Radisson Blu hotel and have a drink or a snack there. Much calmer!
Thanks so much - I neglected to pick up liquor this time around because I wasn't sure about bringing it back through security and all that - I forgot about the sealed bags! Definitely doing that next time though
My friend and I travelled together - our flight to Bergen ended up being delayed a half hour anyway so we had plenty of time on our hands before departure
And luckily we didn't have to walk down that crazy long domestic hallway - ours left from the main hallway.
It was another fantastic trip and I can't wait to go back