Turbo tune / Ralph Bertrum continues to make money by efficiently blocking and buffering data set ( vsam mostly ) and saving cycles. So, it may not be as worthless as you'd expect.
Rob Schramm On Fri, May 19, 2017, 8:00 PM Paul Gilmartin < [email protected]> wrote: > On Fri, 19 May 2017 14:45:41 -0700, Gerhard Adam wrote: > > >z/OS doesn't emulate 3390's, the disk technology does. It also does so, > for good reason, because the biggest issue with DASD is differing > geometries. That would affect space allocation and the blocksizes that can > be used. > > > At the very least, it's z/OS that impels a maximum block size of 32760 > while the 3390 suports much larger. > > >Since there is no performance penalty for emulating a 3390, there is zero > incentive for anyone to represent their disks as anything except a 3390. > > > I'm skeptical that layer(s) of emulation incur no performance penalty. > Wouldn't a hypothetical emulated device supporting two 32760-byte > blocks per track, or one 65535-byte block (the CCW count field) do > better? > > Or eliminate an emulation layer and expose the underlying FBA to > the (ststems) programmer. I believe recent OS releases have > (very limited) support for this. An enhanced QSAM could make this > transparent to the application programmer, even as QSAM does for > z/OS UNIX files. > > -- gil > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > -- Rob Schramm ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
