Victor, Are you using DFDSS DUMP or COPY?
The DUMP function will _not_ decompress the data set and will take a physical copy of it. Naturally, as it is already compressed, further compression when copying it to tape will not be very beneficial. Other utilities, such as IEBGENER. have to decompress the data set as they are doing a record by record, logical, copy (this may not be true for IDCAMS when using the compression interface, see II14507). Hope that helps, Yifat -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On Behalf Of Victor Zhang Sent: Tuesday, April 10, 2012 6:01 PM To: IBM-MAIN@bama.ua.edu Subject: Re: Questions regarding SMS compacted dataset Chris, Thanks for the reply. Using dss is to back extended files to tape/virtual tape. Your answer said the data read will be expanded. So even by setting compact as N, the amount of data written to tape/virtual tape will be same, right? My another question is: If I set compact=N for storage class, so data sets will not be compressed/compacted. If I use same utility to copy it to tape/virtual tape, will there any difference for the data stream writing to tape? I already noticed a difference: By enabling compact option in storage class, I have very low compression ratio for data written to tape/virtual tape, do you have any idea? Regards Victor ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
