I somewhat agree that z/Architecture is not "a feature of z/OS", however, access to Principles of Operation is mandatory in order to to write (or even study) assembler code. Numerous other z/OS pubs make many references to Principles of Operation. For example, the statements shown below extracted from page 65 within "z/OS Version 2 Release 4 MVS Programming: Extended Addressability Guide" (SA23-1394-40):
"The purpose of this section is to help you use the 64-bit GPR and the 64-bit instructions as you want to save registers, perform arithmetic operations, access data. It is not a tutorial about how to use the new instruction set. Principles of Operation is the definitive reference book for these instructions." It appears that IBM is a bit inconsistent about how to obtain the z/Architecture Principles of Operation. I thought I would take peek at the z/VM library at: https://www.vm.ibm.com/library/index.html Down on the left hand side of the page is an item labeled "z/VM Related PDFs" which gets you to: https://www.vm.ibm.com/library/other.html If you type "Principles" in the "Filter" box on the resultant page you'll see the download links for SA22-7832-12 (z/Architecture Principles of Operation) and SA22-7201-08 (Enterprise Systems Architecture/390 Principles of Operation). The links work and no IBM user ID is required. Also, on the z/VM Indexed PDF page (https://www.vm.ibm.com/library/pdfzip.html) there is this statement: "Note: Starting with the 2019 April Refresh Collection the z/VM Related PDFs will no longer be included. Please see earlier collections or see the Related PDFs page." Hopefully the "Related PDFs page" will continue to be available. To the IBMers: Any chance on having a similar Related PDFs link on the z/OS home page? Bob
