IBM's brief flirtation with extended real addressing (26-bit addressing) in the IBM 3033, 3081, and a few models thereafter was quirky. IBM pretty quickly dropped extended real addressing once XA debuted.
Back to Tony's original question, I think an "Architectural Level Set" is difficult to define in practical terms because there are different real world ALSes. I suppose one could argue that there are effectively z/VM, Db2 for z/OS, z/OS, Linux, z/VSE, and compiler ALSes, as notable examples. For example, z/VM 7.2, planned for release this month (September, 2020), declared a new ALS which is manifested/instantiated in IBM z13 and higher models, including all IBM LinuxONE models. Red Hat Enterprise Linux 8.x and Ubuntu 20.04 LTS have the same minimum model requirements as z/VM 7.2, although I don't think Red Hat or Canonical use the ALS term of art. ALS is not a meaningless term, though. It simply refers to a particular collection of minimum capabilities that can be technically manifested (in principle anyway) by particular server models at or above particular microcode levels. (Sometimes that last detail matters.) "Server models" can sometimes include non-physical ones. It's not a term I use very often, though. - - - - - - - - - - Timothy Sipples I.T. Architect Executive Digital Asset & Other Industry Solutions IBM Z & LinuxONE - - - - - - - - - - E-Mail: sipp...@sg.ibm.com ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
