Sharedbuffers and WorkMem

Hi everybody,

I have some doubts about sharedmemory and work_mem.

I have a server:

64 GB RAM
2 processors 4 cores each one intel xeon 3 Ghz
expecting 300 users in the same time

So, I put in sharedbuffers the same size my two biggest tables, which
are the most read too. 11 GB + 4 GB. total shared buffers = 15 GB

After that I put 100 MB to each expected user, 300 * 100 MB = 30 GB

So, I used only 30 GB + 15GB = 45 GB total RAM

My doubt is, can I use more RAM for shared buffers? about 30 GB (50% of
total RAM)?

What is the max shared buffers I can use? How can I calculate that?

Thanks,

Waldomiro.