Re: #pages read per I/O?

Thanks, Richard!

Richard Foote wrote:

> Hi Y
>
> Just to expand on what Howard has said.
>
> If you perform a read via a conventional index read, then Oracle will only
> read in one block per I/O regardless of the DFMRC.
>
> If you perform a Full Table/Index Scan, Oracle will attempt to read in DFMRC
> of blocks per I/O. However, what Oracle asks and expects and what the O/S is
> able to deliver could be two quite different things. Check out Steve Adams
> site for a script that determines what the "real" value of your multiblock
> read is http://www.ixora.com.au
>
> V$FILESTAT as Howard has suggested and the report from STATSPACK provides
> statistics of blocks per read and occurrences of index reads vs. full table
> reads.
>
> Cheers
>
> Richard
>
> "Howard J. Rogers" <howardjr2000_at_yahoo.com.au> wrote in message
> news:KI2q9.51535$g9.149794_at_newsfeeds.bigpond.com...
> > Just a semantic aside, but we don't talk 'pages' in Oracle, but 'blocks'.
> > And hence the parameter that governs how many blocks are read in a single
> > I/O is called db_file_multiblock_read_count.
> >
> > Type 'show parameter db_file' in sql plus, and you'll see what it's set
> to.
> >
> > As for an average, have a look at v$filestat.
> >
> > Regards
> > HJR
> >
> >
> > "y" <y_at_y.com> wrote in message news:3DA8B29F.9635C9DA_at_y.com...
> > > I am using Oracle8i EE.
> > > I found only Oracle Server process can read index/data pages into Buffer
> > > Cache. So that means at least Oracle8i EE didn't support asynchronous
> > > read, right?
> > > I want to know when the Oracle Server process need to do read from the
> > > disk, how many pages it can read into Buffer Cache one I/O? How to check
> > > the average number of read pages per I/O?
> > > TIA
> > >
> >
> >
Received on Sat Oct 12 2002 - 22:11:48 CDT