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Re: Compression should have been disabled

Hi Dave -

I think the key is "not possible".  In SAS's view your file was potentially
compressible, but in actuality wasn't.  Whatever algorithm they use didn't
detect your scenario.

My experience is that wide files, especially those with large alpha
variables compress the best.  Narrow files, such as yours with 8 variables,
especially if variables are numeric or narrow width character, don't do as
well.

You would do well to test the results with a subset of your file (10,000
instead of 180 million) before bothering to compress the whole shebang.
Look into "obs=" for your program or datastep options.

Regards

Paul Choate
DDS Data Extraction
(916) 654-2160

-----Original Message-----
From: SAS(r) Discussion [mailto:SAS-L@LISTSERV.UGA.EDU] On Behalf Of DB01
Sent: Wednesday, February 02, 2005 10:22 AM
To: SAS-L@LISTSERV.UGA.EDU
Subject: Compression should have been disabled

Regarding compression in the SAS online doc, SAS will disable
compression if "...not possible for the compressed file to be smaller
than an uncompressed one."  However, I've experienced a number of
occasions where the compressed file was about 50% larger than the
uncompressed version.  Just wondering why SAS did not disable
compression in these cases.  The log below shows such an example:

/******************************************************/
379      data lib._history;
380          set allsort;
381      run;

NOTE: There were 180248070 observations read from the data set
WORK.ALLSORT.
NOTE: The data set LIB._HISTORY has 180248070 observations and 8
variables.
NOTE: Compressing data set LIB._HISTORY increased size by 54.12
percent.
Compressed is 1097986 pages; un-compressed would require 712444
pages.
NOTE: DATA statement used (Total process time):
real time           18:43.88
user cpu time       9:29.72

/******************************************************/


Thanks,
Dave
0
pchoate (2538)
2/2/2005 6:58:21 PM
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