The first machine to implement ESA/370 was the 3090E. This was done via microcode updates (since the 3090E hardware was designed prior to ESA). It was not possible to implement PSF in microcode, so MVS used x'1000' as the data space ORIGIN, Every subsequent machine (starting with the 3090S) implemented PSF, and MVS used 0 as the data space ORIGIN. That is still the case today, unless you specify HIDEZERO=YES on DSPSERV CREATE, in which case the ORIGIN is x'1000' and page 0 is hidden, This is desirable because it avoids PER ZAD events, and gives you a 0C4 abend instead of incorrect results when you accidentally use a bad pointer value in the range 0-FFF.
Jim Mulder z/OS Diagnosis, Design, Development, Test IBM Corp. Poughkeepsie NY "IBM Mainframe Discussion List" <[email protected]> wrote on 08/19/2020 07:01:09 PM: > From: "Mike Hochee" <[email protected]> > To: [email protected] > Date: 08/19/2020 09:07 PM > Subject: Re: Strange S0C4 on z15 > Sent by: "IBM Mainframe Discussion List" <[email protected]> > > Some months ago I asked a question regarding the relevance of the > ORIGIN parm on a DSPSERV macro. During that time I came across older > documentation which referred to low-address protection being in > effect when the PSF (Private Space Facility) was not active. My > limited understanding is that the PSF is active on 'virtually' all > systems. Mr Dissen's post below brought this to mind. > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
