3 ms·

How is z/OS like that?

by skissane 4y ago

PaulHoule 4y ago
The ‘virtual machine’ that’s used on IBM z is hardware virtualization, not a foreign system like Java or Infocom’s z Machine. A mainframe is usually running a hypervisor (VM) and underneath that hypervisor there are various operating systems running, z/OS is one of them. Circa 1989 I was in the Computer Explorers and we got to use VM/CMS on an IBM 3090 which is basically a single-user OS a lot like MS-DOS (though it is really the other way around.). To do software development on such a beast you would create a VM and log into it. Of course you can run Linux or Java applications in a VM on z too so you can consolidate legacy applications on the same server with more mainstream workloads.
- skissane 4y ago
  z/VM and PRSM aren't in the same category as System/38, AS/400 Lisp machines, stack machines, the iAPX 432, Common Lisp, the JVM, Burroughs Large Systems, etc. z/VM and PRSM are just virtualising (relatively) mainstream hardware, fundamentally no different than what VMware/Xen/KVM/VirtualBox/HyperV/etc do. The rest are either (1) hardware architectures whose ISAs are much further from mainstream than 360/370/390/z is–aiming to provide high-level capabilities which are normally provided in software, making the distance between the hardware ISA and HLLs much smaller than normal; (2) software architectures which could be implemented in hardware (and occasionally were) to become instances of (1).
pjmlp 4y ago
By having Language Environments.
- skissane 4y ago
  z/OS LE doesn’t do much more than what the C runtime library on Unix or Windows does. Despite the common name, z/OS LE has little in common with IBM i ILE. They do share some code (CEE), but the code they share is just that “C runtime library” part-which actually runs (or ran) on OS/2 as well. The whole “hardware abstraction” part of ILE (MI bytecode) is not part of z/OS LE

3 ms·

How is z/OS like that?

by skissane 4y ago

How is z/OS like that?

PaulHoule 4y ago
The ‘virtual machine’ that’s used on IBM z is hardware virtualization, not a foreign system like Java or Infocom’s z Machine. A mainframe is usually running a hypervisor (VM) and underneath that hypervisor there are various operating systems running, z/OS is one of them. Circa 1989 I was in the Computer Explorers and we got to use VM/CMS on an IBM 3090 which is basically a single-user OS a lot like MS-DOS (though it is really the other way around.). To do software development on such a beast you would create a VM and log into it. Of course you can run Linux or Java applications in a VM on z too so you can consolidate legacy applications on the same server with more mainstream workloads.
- skissane 4y ago
  z/VM and PRSM aren't in the same category as System/38, AS/400 Lisp machines, stack machines, the iAPX 432, Common Lisp, the JVM, Burroughs Large Systems, etc. z/VM and PRSM are just virtualising (relatively) mainstream hardware, fundamentally no different than what VMware/Xen/KVM/VirtualBox/HyperV/etc do. The rest are either (1) hardware architectures whose ISAs are much further from mainstream than 360/370/390/z is–aiming to provide high-level capabilities which are normally provided in software, making the distance between the hardware ISA and HLLs much smaller than normal; (2) software architectures which could be implemented in hardware (and occasionally were) to become instances of (1).
pjmlp 4y ago
By having Language Environments.
- skissane 4y ago
  z/OS LE doesn’t do much more than what the C runtime library on Unix or Windows does. Despite the common name, z/OS LE has little in common with IBM i ILE. They do share some code (CEE), but the code they share is just that “C runtime library” part-which actually runs (or ran) on OS/2 as well. The whole “hardware abstraction” part of ILE (MI bytecode) is not part of z/OS LE