Some things work but are "unreliable" which to me is tantamount t0 not really 
working so you should plan otherwise for what to do instead to mitigate the 
issue if you need it.  This is a partial list because I would need to go 
through my notes thoroughly to be absolutely sure.  
You can do almost everything assuming you have ALL of the updated PTFs to 
support the z16, the problem is not only obtaining those PTF's, but realizing 
that just because the updated software will execute doesn't mean it will work.  
At this point getting IBM to supply the PTFs to you will be part of the 
problem, but when necessary you probably|might be able to obtain them from some 
other sites (that's what I needed to do a couple times).  Occasionally I have 
found that I was able to "lift" software from newer versions of z/OS and it 
would execute fine with the old z/OS 2.2.  The trick is having places to "lift" 
it from.

The areas that you will have the most problems will be with OSA  (OSC and OSD, 
especially the OSC ones) and the 25GB interface express 7s's, if you have 10GB 
express 7s you will likely be fine without the special PTF's.  The same is true 
for the OSE's with the 4 port feature.

If you expect to use SMC-R, then you might want to reconsider because while 
it's supposed to be supported with some extra PTF's, it doesn't work reliably. 

zHyperlink will not work.

Peer mode channels won't function.

CF level 25 is supposed to work, but it too is unreliable, but you can run an 
older level until you can fully convert.  CF duplexing is also unreliable. 

Virtual Flash Memory is unreliable.

IEPF (Instruction Execution Protection Facility) is not fully functional and if 
you have software the absolutely needs it, you should plan otherwise.

RMF works, but many fields and features will not, (mostly parts of the data 
gatherer).  Typically it's only a big deal for performance tuning weenies, and 
moving to a z16, performance shouldn't be an issue (at first).

System recovery boost will not function. 

Sort acceleration boosting will be erratic.  While there are PTF's to address 
some of the issue, it's likely best to just turn it off or live with the 
strange way that it sometimes works and sometimes doesn't.  You won't have any 
errors because of the issues, but sometimes it just won't get the acceleration. 

None of this counts the z/16 features that simply aren't supported in z/OS 2.2, 
and it really shouldn't matter (as much) because you didn't have them before so 
not having them after the move to the z16 should not really cause you any big 
issues (unless you were expecting a lot of processor constraint relief).  Just 
know that some features and microcode just won't be used|usable because 2.2 
doesn't support them.  It won't affect whether you can execute things, only how 
fast they execute.

There is likely more that I'm missing, but I would need to look through my 
notes to be sure and they are literally thousands of pages long.  

I have migrated to z15 and z16 processors from 2.2 (and 2.1) at more than 20 
sites in the past 2 years and have run into just about every problem that can 
come up, and they will.  Just remember to always have a plan for what to do 
when something doesn't work because IBM will NOT help you out.  They will "try" 
but they don't have the caliber of personnel that they used to and the support 
structure to deal with z/OS 2.2 is simply not very large to begin with and gets 
smaller with each passing day.  

In the end, you should be able to get it up and running but your performance 
will not be anywhere close to what you would expect from the vastly faster and 
more capable box than your old one (I don't even know what that is to begin 
with), because a LOT of features of the new box are performed with microcode 
and CPU assists that 2.2 just has zero idea how to invoke. 

Strangely enough even the zIIP processors will not seem as capable.  However 
once you fully upgrade to some newer level (2.5 or 3.1), you will see the 
missing extremely large boost.  

It should take you about a day at most (once you have all of the current 
maintenance on) to get things ready to IPL.  There will likely be a few issues 
for the first IPL, and for the most part they can (mostly) be ignored as it 
will mostly be complaining that "something" seems wrong, but things will 
execute and you should even see a small performance boost on the z16, but don't 
expect to be dazzled.  

Depending on the hardware you are installing (OSA, crypto, etc.) and what old 
non-IBM vendor (and even the IBM stuff) you will run into some odd problems, 
but they are all addressable to the point where things will work,  The IBM 
issues will likely be easier to deal with than the non-IBM ones, because those 
vendors don't have much to gain from helping you out.

Do you know what the plan is for after z/OS 2.2 is up and running?  How long do 
you expect to have to support it before you can migrate to 2.5 or 3.1?  Things 
are similar enough (systems programming wise) that you should be able to 
migrate within a couple weeks for the main OS, and possibly a little longer 
time for the non-IBM software (depending on what it is) because not all vendors 
are good at getting things to work when the platform is not exactly 
"supported", but in the end there are always ways to get things functional.  

I literally have about 10,000 problems and fixes that I compiled while doing 
the many conversions over the past several years, going all the way back to 
migrating from OS/390 to z/OS, and believe it or not, in 2024 I converted a 
site from OS/390 1.8 to z/OS 2.4.  They had older software that kept them from 
2.5 or 3.1, but about 4 months after the conversion I migrated them to 3.1 in a 
weekend. 

Just remember that you need to plan it all out and then just execute the plan.  
The size of the site is almost irrelevant, except that the larger the site, the 
more F.U.D. and flack you get from people who just don't want to migrate.  
There will always be one (or some), but you have to plan to go around or over 
them when the time comes. :)

If you want to discuss this a bit, feel free to contact me offline, I'm sure 
these people don't want me to bore them any more than I already have here. :)

Brian

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