Re: buffer cache and direct reads

On Fri, 16 Jul 2004 20:29:11 +0000, Jonathan Lewis wrote:

>
> The OP seems to be talking about Parallel Query.
>
> When a PX slave does a tablescan or index fast full scan,
> it uses 'direct path reads', which do, indeed, go into local
> memory, and bypass the buffer cache; and do get recorded
> in v$sysstat et. al. as "physical reads direct".
>
> It is still possible for such blocks to appear in x$bh though,
> as other SQL may be querying or modifying the data.
> It is possible for PX slaves to read data (such as partitioned
> tables, or indexed accesses into secondary tables driven
> by the parallel scan) into the buffer cache.

You, of course, are right. I have the latest marvel produced by Kirti and Gopal on my desk, and they seem to concur with you. It is just like Anjo's document about wait events in version 7, but on steroids. Great book!

-- 
A city is a large community where people are lonesome together.