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 

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                      
The PostgreSQL Company - Command Prompt, Inc.

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