Load a database into memory

Hi,

To increase the performance of my database, I tried to tune options.
So I disabled fsync(), increased the shared memory on my Linux AND on 
PostGreSQL.
But I'd like to know if it is possible to load the database into memory 
or maybe is there other options that can change the memory use ?

What else should I know about memory with PostGreSQL ?

I'm open to any suggestion,

Many thanks...

Guillaume.