Check total size of Ram/Memory For Each Database :
select decode( grouping(nm), 1, ‘total’, nm ) nm, round(sum(val/1024/1024)) mb
from
(
select ‘sga’ nm, sum(value) val
from v$sga
union all
select ‘pga’, sum(value)
from v$sysstat
where name = ‘session pga memory’
)
group by rollup(nm)
The Orginial Post from Tom Kyte.
Thank you
Osama Mustafa