FRA parameters in RAC

Hi,

are the parameters db_recovery_file_dest and db_recovery_file_dest_size instance parameters or database parameters ?

I am thinking about these setting in the context of RAC. In particular if these are Instance Parameters, I cannot see how they could be set differently on each RAC instance ?

If they are Instance Parameters then theoretically each RAC node / nstance could have a different setting for these - I am just not sure how that could really be viable ? Would RAC prevent this

thanks,

Jim