Re: Index Fast Full Scan and associated wait

EscVector wrote:
> Jonathan Lewis wrote:
> > "EscVector" <Junk_at_webthere.com> wrote in message
> > news:1168531840.130757.22890_at_77g2000hsv.googlegroups.com...
> > > I'm bottlenecked on db file sequential read. What wait should I expect
> > > to see if the plan shows Index Fast Full Scan? Is it db file
> > > sequential read or scattered read since the Fast Full Scan is treated
> > > like a tablescan and uses multiblock reads?
> > >
> >
> > Typically "db file scattered read"
> > see
> > http://jonathanlewis.wordpress.com/2006/12/15/index-operations/
> >
> > --
> > Regards
> >
> > Jonathan Lewis
> > http://jonathanlewis.wordpress.com
> >
> > Author: Cost Based Oracle: Fundamentals
> > http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html
> >
> > The Co-operative Oracle Users' FAQ
> > http://www.jlcomp.demon.co.uk/faq/ind_faq.html
>
> Thank you for the replies and sanity check. I had expected db file
> scattered reads, but not what I'm seeing. Need to look further.

It seems there may be 2 causes - either plan is wrong and actually you don't do IFFS or most of index is in the buffer cache.

BTW it is interesting how far Table full scan and IFFS can go away from scattered reads to sequential reads? Is there possible situation when Full scan or IFFS is performed only using sequential reads?

Gints Plivna
http://www.gplivna.eu Received on Fri Jan 12 2007 - 05:03:36 CST