<snip> An instruction with a zero base does not use the AR associated with the index, so why won't it refer to the wrong AS when in AR mode? </snip>
I suggested it was a valuable technique, not that it was a valuable technique for accessing data spaces or other address spaces. It is a valuable technique for accessing data that you know is in the primary address space, saving you from having to set an access register. Peter Relson z/OS Core Technology Design
