The IBM Dallas development system has VM volumes mounted read-only to the z/OS client machines. I know zero details of the CP side but I see it from the z/OS side. IBM has shared SYSRES-type volumes for multiple clients. Yes, z/OS reports I/O errors if it tries to write to them, but it all works, and obviously IBM knows what they are doing.
The point is Yes, a z/OS read-only disk is possible. I don't think z/OS "knows" it is read-only, so it tries to write and reports errors, but it survives just fine. Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of John McKown Sent: Tuesday, July 13, 2021 1:31 PM To: [email protected] Subject: Re: Can I define a disk as read only to z/OS? z/OS does not have the concept of a readonly disk. The z/OS mount command will allow the USE=PRIVATE option. But that is not readonly. In the past, under z/VM, I would use a full pack minidisk with I defined in the directory as readonly. This worked, but did cause I/O errors to be reported on z/ OS when it tried to update the date stamp in the VTOC entry for DSNs when they were OPENed. On Linux, there is a readonly option on the mount command for a filesystem. On Tue, Jul 13, 2021, 13:40 Colin Paice <[email protected]> wrote: > I am migrating to the latest levels of ADCD ( C4* instead of A4*). During > the migration I would like to be able to mount the A4* volumes on the C4 > system, but mount them read only. > I can change the Linux disk to be access mode 444, but if I want to IPL > from A4* I need to change it back again. > The z/OS documentation mentions usingn read-only disks, but I can't see how > to do it. I dont think I can do it from the HCD > OA50068: NEW FUNCTION - PROVIDE READ-ONLY ACCESS FOR SYNCHRONOUS PPRC > SECONDARY DEVICES <https://www.ibm.com/support/pages/apar/OA50068> Looks > like it is only for PPRC. > Do I just have to live with changing the access mods to/from 444. > Colin > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
