I wanted to add that the list of facilities mentioned in one of the posts

>ARCH(10) (xC12) execution-hint facility, the load-and-trap
>facility, the miscellaneous-instruction-extension facility, and the
>transactional-execution facility.

leads to some interesting points.

The availability of an instruction on the machine (which the facility bits 
indicate) do not necessarily correlate to whether you may use them.
When there is operating system support needed, there are often "function 
bits" that an application is expected to use to determine availability.
We have tried to improve the IHAFACL documentation going forward to help 
identify those bits that correlate to facility bit(s).

Transactional execution facility is one of interest. It is available only 
on certain z/OS releases (z/OS can run on a zEC12 on more releases than 
those z/OS releases that support the instruction).

Further, it is not available on any z/OS release if z/OS is running under 
VM. 

Thus, for example, running on z/OS 2.2 on a zEC12 does not mean that you 
can use transactional execution if you might be under VM. 
Apparently C/C++ users are supposed to understand this and not try to run 
something that is ARCH(10) if running z/OS under VM if they might have 
coded something that led the compiler to generate instructions that are 
part of the TEF.

Peter Relson
z/OS Core Technology Design


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