Re: Oracle Compression

yuvalyuval wrote:

> Hi,
>
> I would like to compress some Oracle tables to see how well they can
> compress. Is there some sort of a guide or rules for how well tables
> can compress based on their datatypes? I know that some of our DBA's
> have managed to compress tables up to 70%.
>
> What tables if any shouldn't be compressed? Are there datatypes that
> compresses better or is it block related only?
>
> I would like to understand and decide which tables should be compressed
> without testing each table.
>
> Thanks,
>
> Yuval

Compressed tables don't compress in the manner in which you are thinking. Compressed tables compress by eliminating duplications. Thus the amount of compression can range from 0% to 90% or so dependent entirely upon the data. Test.

The perfect table to compress would be something like this:

STATE_PROV     CITY            			  POSTAL_CODE
Quebec         Saint-Jean-Baptiste-de-Nicolet     J3T 1R1
Quebec         Saint-Jean-Baptiste-de-Nicolet     J3T 1R2
Quebec         Saint-Jean-Baptiste-de-Nicolet     J3T 1R3
Quebec         Saint-Jean-Baptiste-de-Nicolet     J3T 1R4
Quebec         Saint-Jean-Baptiste-de-Nicolet     J3T 1R5

-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)