According to Aster and Seidman in "Professional SAS Programming Secrets", "If a file is too large to fit in memory all at once, and less than half of the length of the observation consists of key variables, tag sorting is usually much more efficient. It uses less memory, uses less temporary storage space, and runs much faster."

This quote is from the 1991 edition, and they said it holds through 6.06, the last one they tested. I'd imagine it's true for 6.12, but don't know at all about V8.x .

From the V8 windows companion: "The TAGSORT option in the PROC SORT statement is useful when there may not be enough disk space to sort a large SAS data set....Note that while using the TAGSORT option may reduce temporary disk use, the processing time may be much higher. However, on PCs with limited available disk space, the TAGSORT option may allow sorts to be performed in situations where they would otherwise not be possible. "

Personally, I've most often used the tagsort option when storage space has been a major concern.

Doc

richard Simhon wrote:

> SAS-lers, > > Can anyone tell me at what point it becomes more efficient to use tagsort in > a proc sort procedure. I have always been led to believe that on large > datasets with lots of variables, it is more efficient to sort with the > tagsort option. At what point does it become less efficient and is there a > correlation between the number of variables and the number of observations. > > Thanks in advance > > Richard Simhon > Business Analyst > Allianz Cornhill > Tel +(44) 01483 552628 > \\\|/// > \\ - - // > ( @ @ ) > --oOOo-(_)-oOOo-- > > ********************************************************************** > Copyright in this message and any attachments remains with us. It is > confidential and may be legally privileged. If this message is not > intended for you it must not be read, copied or used by you or > disclosed to anyone else. Please advise the sender immediately if > you have received this message in error. > > Although this message and any attachments are believed to be free of > any virus or other defect that might affect any computer system into > which it is received and opened it is the responsibility of the > recipient to ensure that it is virus free and no responsibility > is accepted by Cornhill Insurance PLC for any loss or damage in any > way arising from its use. > > Cornhill Insurance Plc, Registered in England number 84638, > Registered Office 32 Cornhill, London EC3V 3LJ. > > Regulated by the Personal Investment Authority for life and pensions only. > Member of the General Insurance Standards Council for direct general insurance only. > **********************************************************************

-- Lawrence H. ('Doc') Muhlbaier muhlb001@mc.duke.edu Assistant Research Professor Duke University Medical Center 919-668-8774 (office) DUMC 3865 919-383-0595 (home) Durham, NC 27710-7510 919-668-7057 (FAX)