Re: Excessive Logical and Physical I/O

Brian Peasland <dba_at_remove_spam.peasland.com> wrote:
> > So the excessive reads were due to the query having to build a read
> > consistent view of the table blocks.
> >
> > My next question is: Would large rollback segments (i.e. overextended)
> > make this read consistent build process much slower..?
>
> Because Oracle has to go through much more rollback information to build
> a read consistent image of the data! More rollback information to go
> through = larger rollback segments!
>
> > The rollback segments have overextended to nearly 2Gb (2000 extents).
> >
> > Would this have a (noticeable) negative impact on the speed of the
> > read consistent build process...?
>
> Yes. If a user changes 1GB of data and a second user needs to build a
> read consistent image on that 1GB of data, it would take longer than if
> only 1MB of data was involved. More data = more work.

What if the second user only needed to build a read consistent image on 1M out of that 1G?

Xho

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