SIZING SGA

Hello
how much % of RAM (main memory ) we can allocate
for Oracle SGA on a windows NT/2000 servers. i mean
how we will determine the SGA componets sizes when we
install oracle on a windows/unix servers.
please give some bench mark /thumb rules.
thanks
Rao chelli

If Oracle is the only application on your server, my rule of thumb is 35 - 40% of RAM goes to the SGA.