Re: High Water Mark Question - Reposted

In article <80gtmn$aq$1_at_news2.tor.accglobal.net>,   "John Chiu" <johnymc_at_netscape.net> wrote:
> The HWM will remain the same.

However, Oracle is not completely clean when deleting. A few bytes here, a few bytes there, it will eventually fill up the data blocks and start increasing the high water mark, and slow down full-table scans. Whether this happens in a human time scale depends on the exact config. If row-chaining occurs you have a big hit.

See Advanced Oracle Tuning and Administration for some other scary stuff, like SQL*Loader Direct path loading above the high watermark, and an odd comment about how the newly free blocks are placed at the bottom of the free list, so inserted records will be added beyond existing records (to oversimplify but hopefully clarify, imagine the high water mark at block 990, and blocks 991-999 on the free list. Deleting all the records in blocks 1-989, you would wind up with a free list starting with... 991).

>
> John Chiu
>
> Anurag Minocha <anurag_at_synergy-infotech.com> wrote in message
> news:382BC8CC.B5FAD1BC_at_synergy-infotech.com...
> > Hi ,
> > I have a question that suppose we have 1 lac rows in a table , the
HWM
> > is set to a particular value. Now i delete 75000 of the rows the HWM
> > still remains the same.Again if i insert some 70,000 rows will the
HWM
> > increase or will it remain the same.
> >
> > I have to follow this procedure everyday in our database and am
worried
> > whether performance will go down or not.
> >
> > reply at
> > anurag_minocha_at_hotmail.com
> >
> >
> >
>
>

jg
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Before you buy. Received on Fri Nov 12 1999 - 11:30:20 CST