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