Praveen Kumar N wrote:
> Hi,
> can anybody explain me what is the difference between system cache
> and buffer cache?
>
> I found that keywords in PostgreSql FAQ
> http://www.postgresql.org/docs/faqs.FAQ_DEV.html#item2.1
Another important cache is the "relation cache", relcache for short,
which is also stored in local memory.
One important point about these (relcache, syscache, catcaches = catalog
caches) is that they are invalidated using the "sinval" system, which
passes messages from one backend to all others via a queue in shared
memory. The buffer cache needs no such thing, precisely because it
lives in shared memory. But it needs to be protected by locks.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
