> Date: Mon, 25 Oct 1999 18:22:11 -0500 > From: mp <mpwelch@SPRINTMAIL.COM> > Subject: Re: Version 8 compression > > Compressors,

> Under Windows, SAS Compression can result in reduced elapsed times due to > reduced I/O activity, under MVS it appears compression is more costly > although I have yet to complete a multi-platform SAS compression study.

In general, compression is a trade of one resource for another. It turns out that there's often a side benefit however.

The raw tradeoff is disk space for CPU utilization: reading compressed SAS datasets requires more CPU than reading uncompressed data.

The side benefit is fewer disk I/Os. Because the data occupy less space, fewer reads are required to input them.

This means that using SAS compression (when it actually results in smaller datasets) tends to have four effects:

- Smaller datasets. - More CPU utilization. - Less disk I/O. - Shorter "wall clock" time.

Because PC users tend to watch wall time, it is the most noticable effect. Because mainframe users tend to get dinked for CPU seconds, they'll not usage here. On Unix, everything's free, but we have tools to watch wall time, cpu time, and I/Os, so we see the whole, true, picture <g>.

-- Karsten M. Self (kmself@ix.netcom.com) What part of "Gestalt" don't you understand?

SAS for Linux: http://www.netcom.com/~kmself/SAS/SAS4Linux.html Mailing List: body "subscribe sas-linux" mailto:majordomo@Cranfield.ac.uk