Dear SAS-L-ers,

Steve Steve posted the following:

> I think that there is a system compression option on our Unix system
> and sometime I get the following warning message. I would like to
> remove the warning. How can I do it, please?
>
> WARNING: Compression was disabled for data set WORK.XXX because
> compression overhead would increase the size of the data set.
>
Steve-squared; whoa doggie!  You do not want to disable that warning, it is telling you something very important.  If you were able to override the warning and actually compressed the data set, it would end up bigger than it was in its uncompressed state.

You see, SAS looks for adjacent redundancy in observations it is going to compress.  It compresses them down to 2 or 3 byte representations, _AND_ adds a compression control header field; which in mainframe environments is 12--count 'em: twelve--bytes long.  (Nah, I don't know the length on UNIX, Linux, Windows, etc., so don't ask me)  So, if you have observations that do not have a lot of adjacent redundancy, the addition of the control header field would make the observation bigger than it originally was... precipitating the very WARNING that you are thinking of "removing".

So, what do you think Steve-squared, can you live with that warning and live with SAS data sets that don't compress down?  I'll bet that the answer is a resounding YES!  If not, then reordering the data to achieve adjacent redundancy may be in order.

Steve Steve, best of luck in all of your SAS endeavors!


I hope that this suggestion proves helpful now, and in the future!

Of course, all of these opinions and insights are my own, and do not reflect those of my organization or my associates. All SAS code and/or methodologies specified in this posting are for illustrative purposes only and no warranty is stated or implied as to their accuracy or applicability. People deciding to use information in this posting do so at their own risk.

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Michael A. Raithel
"The man who wrote the book on performance"
E-mail: MichaelRaithel@westat.com

Author: Tuning SAS Applications in the MVS Environment

Author: Tuning SAS Applications in the OS/390 and z/OS Environments, Second Edition
http://www.sas.com/apps/pubscat/bookdetails.jsp?catid=1&pc=58172

Author: The Complete Guide to SAS Indexes
http://www.sas.com/apps/pubscat/bookdetails.jsp?catid=1&pc=60409

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Managing is like holding a dove in your hand. Squeeze too hard
and you kill it, not hard enough and it flies away. - Tommy Lasorda
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