Oracle-L: RE: Oracle Compress Option

From: Khedr, Waleed <Waleed.Khedr_at_FMR.COM>
Date: Thu, 25 Sep 2003 06:34:47 -0800
Message-ID: <F001.005D10C3.20030925063447@fatcity.com>

Something else I forgot, full segment scans becomes faster, since he segment is 70 percent smaller.
So this could help balancing resource utilization between the CPUs and IO.

Waleed

-----Original Message-----
Sent: Thursday, September 25, 2003 9:50 AM To: Multiple recipients of list ORACLE-L

Waleed, I get your point ...

We have 6 RAC instances that run active-active ... and compared to availability requirements, we (incl management) decided that disk is cheap.

I guess it is relative ...

Raj

Rajendra dot Jamadagni at nospamespn dot com All Views expressed in this email are strictly personal. QOTD: Any clod can have facts, having an opinion is an art !

-----Original Message-----
Sent: Thursday, September 25, 2003 9:35 AM To: Multiple recipients of list ORACLE-L

Disk is not cheap if you pay for high availability configuration. I compress historical data on daily basis and was able to save 70 percent of the disk space. Imagine the amount of savings for five TB.

Two major issues:

Oracle says updates will be slow on compressed tables, but I say don't even try to update a compressed table, uncompress first otherwise you will end up with a segment that is not good at all for scattered reads.
You can not add columns to the table when it's compressed, so if you compressed a big table and need a new column you need to recreate the table without compression. So adding many extra columns before compression is a good idea.

It's mainly good for data warehouses applications.

Regards,

Waleed

-----Original Message-----
Sent: Thursday, September 25, 2003 9:05 AM To: Multiple recipients of list ORACLE-L

I think 9202 doesn't like to export compressed tables in direct mode ... so watch out for that ... I implemented, tested and next day reverted back to regular tables due to this export issue. Disk is cheap.

A BAARF party member wannabe !!
Raj

Rajendra dot Jamadagni at nospamespn dot com All Views expressed in this email are strictly personal. QOTD: Any clod can have facts, having an opinion is an art !

-----Original Message-----
<mailto:mln_at_miracleas.dk> ]
Sent: Wednesday, September 24, 2003 10:05 PM To: Multiple recipients of list ORACLE-L

"Compress to impress?" by Julian Dyke is a good presentation on this topic (see for instance http://www.ukoug.org/calendar/jan03/jan30ab.htm <http://www.ukoug.org/calendar/jan03/jan30ab.htm> ).

I do have the article - 202 K with no compression, 147 K with compression :).

Let me know if you're interested, and I'll email it directly to you.

Mogens

Avnish.Rastogi_at_providence.org wrote:

>Does anybody has any experience with Oracle 9I compression option. I did
some test on 9202 with a table of more 14 million rows. Table has total 7 indexes. Surprising both table and indexes are using more space after compression. Before compression space used is 13064MB and after compression 13184MB. In both the cases I did export from source table and stored in two different tablespaces. Any insight on that and any disadvantages of using that.

>
>Thanks

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Author: Khedr, Waleed
  INET: Waleed.Khedr_at_FMR.COM

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Received on Thu Sep 25 2003 - 09:34:47 CDT