Re: Reac-Cache-Rate of a Data Warehousing System

From: "David Grove" <david_grove@health.state.ak.us> > >I'm wondering why achieving >95% read cache rate in a data warehouse would >be considered undesirable? Suppose you had several GB of shared memory. >You might be able to cache whole tables, or in a small warehouse, maybe >even >cache the whole thing. Light scans are fast, but isn't reading from memory >even faster? OK, OK, it was a sweeping generalisation. :-) Sure you *might* be able to cache whole tables, but certainly not on any of the systems I've written recently. Most times it's just better to forget about all the OLTP stuff and go for broke on the virtual memory... >Obnoxio The Clown <obnoxio@hotmail.com> wrote in message >news:7tab13$t1s$1@news.xmission.com... > > > > From: leekb@bigfoot.com > > > > > >Have a couple questions here, > > > > > >In the Informix Performance Guide, a >95% read cache rate is normal and > > >definitely achievable in a transactional system/environment. > > > > In a *transactional* environment, yes. > > > > >Considering the vast amount of data read/written in a data warehousing > > >system, is it practical having the BUFFERS the size of the huge amount > > >data read by a query statement? > > > > Probably not. You'd probably want to reduce your buffers and make use of >PDQ > > memory instead. > > > > >On the same light, is achieving >95% read cache rate on such a system > > >practical? > > > > Probably not. It might be possible, but it probably isn't desirable. > > > > ______________________________________________________ > > Get Your Private, Free Email at http://www.hotmail.com > > ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com