Re: Buffer gets

From: Howard J. Rogers <howardjr2000_at_yahoo.com.au>
Date: Mon, 8 Sep 2003 16:56:44 +1000
Message-ID: <3f5c289c$0$10356$afc38c87@news.optusnet.com.au>

"Francesco" <franz_at_mail.com> wrote in message news:TGV6b.300833$Ny5.9356668_at_twister2.libero.it...
> Hi all,
> I'd like to know what exactly means the column BUFFER_GETS
> in the view v$SQL.
> Is it the number of blocks "filled" by a query in the buffer cache ?
> Thanks a lot
> Francesco
>

It's the number of times you've walked into the buffer cache hoping that the data you want is already there (ie, cached). If it is, you can read it from memory, without having to disk I/O (a 'buffer get hit') and if it isn't, you have to drop down to disk to fetch it (a 'buffer get miss').

In a nutshell, the number of gets is how many Oracle blocks needed to be interrogated to satisfy a particular query, whether they came from disk, or were already in memory.

A lot of people get worked up about the ratio between the hits and misses. But they probably shouldn't. One of the main things is to minimise the number of gets in the first place (ie, write cheaper, more efficient, SQL), regardless of whether you get hits or misses on them.

Regards
HJR Received on Mon Sep 08 2003 - 01:56:44 CDT