For a developer and a user it's nearly the same, for mainframe programming it's 99% the same, but yes no LPAR's and no z/Linux...sure. But to learn how the core

For a developer and a user it's nearly the same, for mainframe programming it's 99% the same, but yes no LPAR's and no z/Linux...sure. But to learn how the core of mainframes work (as of today), that's the tool/distro. BTW LOTS of MVS code still lives in z/os