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Re: Oracle Compress Option

From: Tanel Poder <>
Date: Thu, 25 Sep 2003 06:49:47 -0800
Message-ID: <>

RE: Oracle Compress OptionHi!

I think in DW style environments, compressed fact tables and indexes on them can give more benefit than just saved disk storage -> if you save 50% in space due compression, then 100% more data can be read in single IO as well.


  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:

  1. 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.
  2. 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.



    -----Original Message-----
    From: Jamadagni, Rajendra []     Sent: Thursday, September 25, 2003 9:05 AM     To: Multiple recipients of list ORACLE-L     Subject: RE: Oracle Compress Option

    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 !!

    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-----
    From: Mogens Nørgaard []     Sent: Wednesday, September 24, 2003 10:05 PM     To: Multiple recipients of list ORACLE-L     Subject: Re: Oracle Compress Option

    "Compress to impress?" by Julian Dyke is a good presentation on this     topic (see for instance

    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 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.


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Author: Tanel Poder

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Received on Thu Sep 25 2003 - 09:49:47 CDT

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