[exim] Hints in Ram

Hi,

I have two questions.

i/ If I put the hints db in RAM what size should I make the RAM disc?
I'm thinking along the lines of 2G. The system has more than enough RAM
and could push this to 5G if needed.

ii/ What happens if the RAM drive fills up?

If anyone can advise me on this it would be much appreciated.

Thanks

David