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It's doing that because it ISN'T reading
a sequential set of blocks. In my example
(taken from your original list) block 14,709
is presumably already in the buffer, so
Oracle has to read up to it, (which takes
three blocks), skip it, and then start again
at the block after.
Arguably it might be a better strategy for
Oracle to allocate an 8-block multiblock
object and always read 8 blocks into,
then 'free' any that are already in the buffer.
But it doesn't - and there may or may not
be a very sensible argument why not, it
might simply be an accident of history.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
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The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
> Thanks Jonathen ,
> But what I am pointing to is , why it is reading 3 blocks first time
and
> then 8 blocks next time , why not 8 blocks always .
> Look at p3 which is no of block read .
>
> >
> >
> > Here is a part of trace file . I am finding that oracle is trying
to
> > read 8 or 3 or 7 blocks at a time . But block numbers are all
> > sequential i.e. it will read 3 blocks starting from 14706 and then
8
> > blocks starting from 14710 ( 14706+3 ). Why it doesn't read 8
blcoks
> > always it multi_block_read is set to 8 ? Any Idea .
> > Also what is ela=1 ,does it mean elapsed time is 1 sentisec ?
> >
> >
> >
> > WAIT #32: nam='db file scattered read' ela= 0 p1=4 p2=14706 p3=3
> > WAIT #32: nam='db file scattered read' ela= 1 p1=4 p2=14710 p3=8
-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Jonathan Lewis INET: jonathan_at_jlcomp.demon.co.uk Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Fri Mar 14 2003 - 15:39:08 CST