Compression/compaction is done in the controller/FICON Adapter, if it is turned ON in either SMS, a parmlib member, or JCL (DBB=TRTCH=COMP). 2-3:1 is achieved on average. It's important, because it will affect the performance of the VTS, and tape usage (capacity).
Roger S. -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Scott Chapman Sent: Thursday, July 18, 2013 5:51 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: RMM v/s TS7740 VTS The compression is done after it hits the VTS, and is compressed in the disk cache. My possibly faulty memory says that it at least used to be done on the host adapter cards in the VTS (that have the FICON connection to the mainframe), but that may not be entirely accurate. But effectively: mainframe FICON Adapter -- 100GB --> VTS FICON adapter --> 25 GB --> VTS Disk --> ~25GB --> VTS Tape I haven't taken the time to really understand RMM and how it reports things though. Sorry. Scott Chapman On Wed, 17 Jul 2013 18:01:34 -0500, Munish Sharma <mf291...@gmail.com> wrote: >Hello >I am researching on TS7740 VTS, as it reaching the VTS Throughput limit and >done some initial analysis with VEHSTATS. >To narrow down to alias level reporting, for who is using how much at what >point of time..I am using RMM report. I am struck at a point, where I do not >understand.. if RMM says in panels a DSN is 100GB, but in RMM report DSIZE is >zero (most cases) .. and comparatively minimum data(lets say 6-7 GB), under >Variable(Actual amount of Data on Tape) .. in RMM report. > >So, If RMM Panels says TAPE DSN was 100 GB.. but 6-7 GB on real tape.. I >understand compression does that.. > > >NOW the question is ... DOES VTS do any I/O initially while creating 100GB or >is it compressing while write to VTS and not creating 100GB( just fake it ).. >So does that do I/O for 100 GB while writing to VTS or 25gb as if compressed? > >Another scenario.. If a Compressed Data on Backend tape was 3982 MB and 25244 >MB in VTS.. after coming to VTS .. Does this DSN uses 25 GB space in VTS or >virtualization keep it at 3982 MB even in VTS (just fake it)... So, when Host >going to read it back, does it read 25GB, or 3982 MB? > > >Please let me know, how to look at it.. > >Regards >Munish Sharma > >People are Awesome.... > >---------------------------------------------------------------------- >For IBM-MAIN subscribe / signoff / archive access instructions, send >email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
