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Glossary

Many terms used by maniframers are acronyms, assumed to be already known and in the daily working language of end users. For people coming to the mainframe world, this can be quite confusing. This document serves as a 'Rosetta Stone' for translating mainframe-speak.

Distributed

"Distributed Systems" is a term for non-mainframe stand-alone computers, often derived from 'desktop' PC architectures:

  • Intel and AMD x86, standard PC archiecture, 32-bit mode being largely obsolete but still commonly found in use

  • Intel and AMD x86_64, 64-bit PC architecture, capable of running 32-bit mode x86 programs, most of which are also capable of running virtualization programs (hypervisors), such as Xen, Libvirt, and the proprietary VMWare

  • Intel IA64 (Itanium II), a 64-bit PC architecture, predecessor to x86_64, which cannot run 32-bit x86 programs apart from emulation

Other Distributed

Some non-PC and non-mainframe architectures include the following.

  • P is the 'Power' RISC -- Reduced Instruction Set Computer -- architecture redesign. RISC represented a trend in the hardware processing the instructions, to shrink the nunber of instruction primitives which given semiconductor die or processor chipset needed to implement, and so, to get a net increase of speed, reduction of power needs, and so, more cost effective performance.

  • SPARC (Scalable Processor Architecture) is the RISC architecture from Sun Microsystems (now Oracle)

  • PA-RISC (Precision Architecture - reduced instruction set computer) is the RISC architecture from Hewlett Packard (now HPE)

  • ARM (Advanced RISC Machine, originally Acorn RISC Machine) is the RISC architecture developed by Arm Holdings

AMD/Intel, POWER, and ARM are all supported by the KVM hypervisor, along with Z (mainframe, see below).

Mainframe

"mainframe" is the informal term for IBM "Z" class architecture. Other architectures include "I" and "P", which have mostly merged, and "X" for PC class systems.

  • Z is a succession of mostly backward conmpatible designs originating from the early System/360 instruction set, represented in a human-readible form in Basic Assembly Language (BAL), and su0rounding ecosystem of I/O Channel Co-Processor design.

An I/O co-processor is designed to receive, at high rate, commands and content data, and so to permit off-loading by the CPU and RAM so that almost all I/O is handled apart from ordinary computation. Regular work (in other runnable queues) can proceed in parallel with the I/O. (CPU workloads are not blocked by I/O workloads.)

The switch in context permits a processor to engage in multi-task processing. This was used in release 360/VM to have a very early (pre Unix) form of three seeming virtual, but seperate task processor spaces (called BG, F1 and F2 -- the Background task, and Foreground 1 and 2 tasks) which was in use in the late 1960's, and has been extended ever since.

Z architecture is supported by the KVM hypervisor, along with AMD/Intel, POWER, and ARM (see above). Z architecture is also supported by IBM's z/VM hypervisor, which is the platform for which ZNETBOOT was designed.

Glossary

  • ASCII: American Standard Code for Information Interchange; see: EBCDIC

  • BAL: Basic Assembly Language

  • BCD: Binary Coded Decimal -- a character set use by IBM on their 1401 series predecessor (discrete transistors and plugboards based), proposed to transition off of Hollerith 'tab' cards encoding a 12 rows, called: A B, and 0 through 9

  • CMS: officially the Conversational Monitor System, a single user operating system packaged with z/VM and used for the majority of housekeeping work in z/VM. CMS provides the interactive environment which defines the user experience when z/VM is employed as an operating system product. CMS includes XEDIT, Rexx, and CMS Pipelines.

  • cURL: local convention, after the network file transfer utility; another example might be wget

  • DASD: Direct Access Storage Device, i.e., "disk"

The majority of DASD for IBM Z systems allows traditional track and record geometry (see "count key data" or CKD or ECKD), but DASD may alternatively be of the more common fixed-block architecture (FBA). Most other computer architectures use fixed-block geometry for all disk types (except floppies). Ironically, major DASD vendors provide track and record geometry (ECKD) by emulation, using fixed-block devices under the covers for the physical backing store.

  • DCSS: Discontiguous Shared Segment; a memory segment (commonly contiguous, despite the name) which can be shared across virtual machines on z/VM. DCSS provides an effective sort-of virtual ROM for z/VM virtual machines. A DCSS can contain a filesystem, and z/Linux has drivers which take advantage of that.

  • EBCDIC: Extended Binary Coded Decimal Interchange Code, IBM's preferred character set for S/390 and AS/400 and successor to BCD. EBCDIC is a character encoding conceptually similar to ASCII but with different (and incompatible) character-to-bit-pattern assignments. Translation between EBCDIC and ASCII is usually done transparently, but some differences occasionally leak out.

  • ECKD: Extended Count-Key-Data is a disk recording format which adds counts and keys to track-and-record disk format. It is derived from CKD. See "count key data".

  • EXEC: in CMS is the filetype for a scripted command. (think shell script) CMS provides three interpreters, the preferred being REXX. To indicate that an EXEC should be interpreted as REXX, the file must start with a REXX comment and thus begin with slash asterisk /*.

  • FOSS: Free and Open Source Software

  • FLOSS: Free/Libre Open Source Software, a variant of "FOSS" with essentially the same meaning.

  • GPLv2: one of several licenses documented by the Free Software Foundation, providing generaly that if one transfers a binary form of software to someone, one must also make the sources and documentation of the methods used to produce it, and to continue that license requirement on the transferee to any later successor or sub-transferee.

  • I/O: input/output, communucation outside of the given processor chassis, as to a punch card reader (1402), line printer (1403), hard drive (3390), console device (3270 or 3215), network connection (OSA)

  • IFL: Integrated Facility for Linux; a ham-strung mainframe processor which can boot Linux and can boot z/VM but cannot boot z/OS or other operating systems. IFLs are priced lower than general purpose engines.

  • IPL: Initial Program Load. This is the IBM mainframe term for "boot".

  • IUCV: Inter-User Communication Vehicle; a service of z/VM for communicating between virtual machines, so named because a "user" on z/VM is a virtual machine and a virtual machine is a user. IUCV is operationally much like named sockets which is process-to-process, but IUCV is VM-to-VM.

VM/CMS and z/Linux support AF_IUCV sockets. On Linux, AF_IUCV is defined across all architectures but is only effective when the architecture is Z and Linux is hosted by z/VM.

  • Linux: specifically, a computer core executive program (kernel) developed initially by Linus Torvalds, and as time passes a commuinity of developers, some completely unpaid, others sponsored by an employer; It is copyrighted, but freely available on terms of a license known as the GPLv2. Generally a shorthand way to refer to an ecosystem of libraries and programs which make that core executive useful in performing general computing tasks

Linux itself is just the kernel, but the name implies also a "userland", a collection of utilities and programs to make the kernel useful. Various Linux distributions (SUSE, RedHat, Debian) provide such utilities, with the exception of Android which uses the Linux kernel to host its own Java-based environment.

  • LPAR: a Logical PARtition is a sectioned-off collection of computing resources reserved for a perticular operating system instance. Think of an LPAR as the hardware work-alike to a virtual machine.

  • NSS: Named Saved System; related to DCSS, a kernel which can be booted by name (rather than booted from a device by address). An NSS can be booted (see IPL), unlike a DCSS which cannot.

  • OSA-Express: Open Systems Adapter; a networking interconnect method used by IBM hardware, and dynamically managable under software control, rather than by setting up a physical Ethernet network of interfaces, patch cables, and network switches. It can perform similar ISO seven layer stack functions, and operates at layers 2 and 3 of that stack. WIthin a single mainframe, it removes the potential for covert interception of network traffic, as there is no point of attack available to a person lacking rights to 'tap' into and 'tee' content off of (passively6 or via active 'spoofing')

  • Rexx: a scripting language widely use by IBM products

  • RISC: Reduced Instruction Set Computer

  • SFS: Shared FileSystem; in CMS, SFS is a filesystem which can be used by several virtual machines simultaneously. Historical CMS filesystems reside on virtual disks which cannot be shared without side-channel locking and related coordination.

  • TCP/IP: one of several protocols for of data transfer between computing devices (Mainframes, CCP devices, remote systems)

  • Unit Record (UR) equipment; 'tab' card based computing; 026 keypunch, 029 key verified, 082 sorter, 5xx series plugboard and patch cable programmed relay based electronic computing devices; successor was the 1401 family and BCD

  • X3270: an IP network console with a variant form of the 'telnet' type of interface; As it dates from an earlier era, there are areas of the screen, called 'fields' in which input mat be typed; the TAB key will advance to the next available field (some fields may be "display only") after the present cursor position. <Enter> customarily submits all of the filled-in fields to the remote server for processing as a transaction. Until <Enter> is selected, one may cycle (tab) and wrap around through all editable fields, and either over-type, or use minimal in-field edit commands

  • VMARC: short for "VM ARChive", is a customer-developed utility for sharing collections of files among z/VM systems, and the format of the collection. It is similar to ZIP and TAR.

  • wget: see: cURL

  • XEDIT: the primary file editor in CMS

  • z/Linux: Linux for Z architecture, a compilation of the Linux kernel and associated "userland" for use on Z series computers, either virtual or physical. It is often said, "Linux is Linux", and the environment seen in z/Linux is nearly identical to that seen in Linux on AMD/Intel or Linux on POWER or Linux on ARM or Linux on MIPS or Linux on SPARC.

Linux on Z series is an ASCII based system.

Linux for Z series is not "Linux for z/OS". z/OS is an operating system. "Linux for z/OS" is a common misnomer and very misleading.

IBM modified z/TPF to support the z/Linux ABI (application binary interface). z/TPF modules can be created on z/Linux and then deployed on z/TPF improving on the development cycle for many programmers.

Other Glossaries

IBM also publishes several Glossaries:

z/VM Glossary

http://publibz.boulder.ibm.com/epubs/pdf/hcsl9c30.pdf

IBM document: GC24-6195-05

There is an excellent and curated 'link-farm' at PDF page 152 (document pagination 143)

Wikipedia Links

https://en.wikipedia.org/wiki/SPARC

https://en.wikipedia.org/wiki/PA-RISC

https://en.wikipedia.org/wiki/ARM_architecture

https://en.wikipedia.org/wiki/Count_key_data