Per master contract. We usually wind up using our once a year transfer to transfer from one of our Master contracts to the other Master contract. If you just have add ons, you don't have to use that once a year transfer.
A transfer is when you move points between contracts. It can be within the same owner if the owner has more than one master contract, but more often it is where one DVC member has excess points and either can't use them, can't bank them or just wants to get rid of them, but does not want to rent them out to someone and take on that responsibility.
In a transfer, you are only transferring the points for that year, not the entire ownership (30-40 years).
As far as offsetting compensation for the value of the tranferred points ? well, that is up to the transferor and transferee.
DVC allows one transfer a year which can be in inbound or outbound transfer but not both. THis prevents DVC members from swapping points to enhance their ability to book at the 11 month window.