Re: question about rollback and redo

how much does redo and rollback go up if you have indexes on the tables when you do deletes? I know they go up when you do inserts and updates?

aside from the additional work to manage the indexes.

"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message news:bkhidg$t4f$1$8300dec7_at_news.demon.co.uk...
>
> (assuming no indexes)
> When you delete a row the row plus about 80
> bytes of overhead gets put into the undo. A
> few bytes of change are made to the data block
> (deleted flag, ITL entry).
>
> The redo then contains a record consisting of
> two change vectors - each with an overhead
> of about 80 bytes. One change vector describes
> the change to the data block, and the other change
> vector describes the change to the redo block,
> which include the detail of the deleted row.
>
> Delete 1MB as 10,000 rows of 100 bytes, and
> you have 10,000 undo records - which is the
> 10,000 rows with 10,000 overheads - and
> 10,000 redo records which is 10,000 copies
> of the row plus about 20,000 lots of overhead.
>
> --
> Regards
>
> Jonathan Lewis
> http://www.jlcomp.demon.co.uk
>
> The educated person is not the person
> who can answer the questions, but the
> person who can question the answers -- T. Schick Jr
>
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>
> "Ryan Gaffuri" <rgaffuri_at_cox.net> wrote in message
> news:1efdad5b.0309191139.5eab5f6d_at_posting.google.com...
> > Documentation isnt too clear on this(or Im just not following it).
> >
> > When you do a delete the entire row is copied to the rollback
> segment.
> > Now if Im deleting 1MB worth of data in the datafile(lets assume
> there
> > is no pctfree or pct used, just data), will 1MB of data be written
> to
> > rollback? Im assuming there will be less due to block header,
> etc...,
> > but how much less?
> >
> > Now when the rollback is written to redo, how much data does that
> > entail? What goes in a 'change vector'? Does the entire row get
> copied
> > twice? Once to the rollback and once to the redo logs?
>
>
Received on Sat Sep 20 2003 - 10:19:16 CDT