Re: Index Compression question - solved, Thanks.

Thanks Andy,

Yes, we are using cbo, and that was why some tasks were much faster than others -
I analyzed only a few tables and indexes after compressing, and only them were ok.
All others were slower than before.

I eventually analyzed one table with most complaints about it, and the problem was solved.
I did not expect this to have *such* an effect, as the indexes were analyzed just some days before,
and I thought that there cant be much difference in between time ... but actually it has.

Thatīs a lession for the day ... always use dbms_utility.analyze_schema( ) after compressing indexes.

Thank You
Jan

"Andy" <andy.spaven_at_eps-hq.co.uk> schrieb im Newsbeitrag news:U_QV9.3519$9R.12107447_at_newsr2.u-net.net...
> Jan
>
> If you're using CBO, the stats for the indexes might need to be rebuilt.
> That could explain why user stuff is slow (Oracle avoiding indexes without
> stats) and a heavy duty task (batch perhaps?) is running faster (it's also
> avoiding an index - this time one that wasn't a help - often the case if
> you're reading a large %age of the table thru the index).
>
> Andy
>
>
> "Jan Gelbrich" <j_gelbrich_at_westfalen-blatt.de> wrote in message
> news:b08kg8$n044m$1_at_ID-152732.news.dfncis.de...
> > Hello,
> >
> > due to most information I have (the doc, some books and NG FAQ),
> > index compression can be good for performance,
> > on compressable indexes only, of course.
> >
> > Last night I compressed half of my indexes (most composites, their
> > cardinalities were good enough to do so),
> > which reduced space requirements as I expected,
> > but today, when all people are at their
> > working places again, everybody complains that I made the whole system
> slow
> > down -
> > expect of one heavy duty task, which runs as fast as never before.
> >
> > I know that there are various reasons why a system can be slow
eventually,
> > but for now I want to make sure that it was not due to my actions ...
> >
> > So my Question is: does index compression have *negative* performance
> > effects ?
> > If so, I would have to rebuild some crucial indexes again with
NOCOMPRESS
> > ...
> >
> > I would appreciate any comments from the experienced gurus ...
> >
> > Jan
> >
> >
>
>
Received on Fri Jan 17 2003 - 05:14:35 CST