How the Spare Area of DVD-RAM and BD-R/RE work.

[smilebomb]

I have some question about Spare Area.

I know the DVD-RAM and BD-R/RE have the Spare Area. I want to know :

1, how them works?

2, when does the Spare Area be written? right after a defect found during writing, after all the write is finished and then write the spare area? same for DVD-RAM and BD-R/RE

3, there is difference between DVD-RAM and BD-R/RE about spare area?

 

thanks in advance.