Re: shared_buffers and effective_cache_size

Zhang, Anna wrote:
> Hi,
> I just got a new Penguin machine with 2 processors and 2G RAM. After
> installed postgres 7.2, I started to modify postgresql.conf to get max
> performance. I read Adm Guide and Bruce's article: PostgreSQL Hardware
> Performance Tuning, in my understanding, shared_buffers is similar to
> Oracle's db_block_buffers, but also sometimes I feel it sounds like oracle's
> SGA. When I reached effective_cache_size, don't know what's that, docs can't
> help, it seems for optimizer, but how big should I set? no feeling! Does
> anyone can compare this paremeter to oracle's so I can understand better.
>
> If I set SHARED_BUFFERS = 131072, what effective_cache_size should be?

My guess is that effective_cache_size is an estimate of the amount of OS
caching memory available, rather than PostgreSQL shared buffers.

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