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. ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
