Clearing customs on a connecting international flight in Beijing?

I am flying Syd to Vienna, changing Air China to Austrian Airlines both on Terminal 3, Beijing Capital Airport. There are 6h between flights. Do I have to pick up luggage and check in again? Thanks. Where I should I check this once I get there? My travel agent think this is not required, as in the most airports this is not required.
So far I did it only once flying via Shanghai a few years ago but the flights were on different Terminals.

Thanks.