Since no one else has said it, aren't you are forgetting your entire DASD farm with all its system control block structures embedded within VTOCs, VVDSs, Catalogs, JES datasets, and some other individual data sets? DASD "Sharing" doesn't just have to be within a sysplex, because sharing doesn't have to be concurrent. Does IBM now guarantee that any changes to these DASD-resident structures are down-level compatible with all prior releases of z/OS with no toleration PTFs even required, or does this only apply if you are within a supported upgrade jump? If toleration PTFs are required, what does this say about system versions no longer supported for maintenance?
You IPL all your processors with back-level versions of z/OS after your DASD has been touched by a later version system, then you are sharing all those structures between those two versions of z/OS, even if not concurrently, whether you run a sysplex or not. Perhaps it takes a deliberate use of new features to force an incompatibility, perhaps not. Maybe some change or update could occur just by putting a volume online or opening a data set from the new system, maybe not. One would certainly hope such compatibility issues would be prominently discussed in the migration documentation for one of the later versions of z/OS, but just because these are rare occurrences doesn't mean it shouldn't be a concern and at least researched. My assumption was always if you go beyond a "supported" jump, IBM doesn't test those scenarios and you are on your own. Perhaps you are familiar enough with z/OS 2.1 through 2.4 to be confident there are DASD-resident control block issues with such a jump, but you seem to be implying that without a sysplex, arbitrary z/OS level jumps could have no compatibility concerns and compatibility research is irrelevant. That certainly has not been true in the past. Joel C. Ewing On 9/4/19 1:23 AM, Brian Westerman wrote: > why? He said that there is no sysplex involved, just what is it that he > would not be compatible with in a fall back scenario between 2.1 and 2.4? > You would be pretty hard pressed to find something that would cause them an > issue, so long as the hardware is compatible with 2.4 they are good to go. I > also believe in being prepared for anything, but there are some things that > are a waste of time. If he were running a sysplex, even then he would > "probably" still be okay, but it's not an issue for him to even have to think > about. > > Brian > > .... > -- Joel C. Ewing ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
