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Linux on System z is the collective term for the Linux operating system compiled to run on IBM mainframes, especially System z machines. The history of operating systems running on IBM mainframes is a notable chapter of history of mainframe operating systems, because of IBM 's long-standing position IBSYS was the tape based Operating system that IBM supplied with its IBM 7090 and This article is about the MIT Computation Center operating system BOS/360 (Basic Operating System/360 was an early IBM Operating system. TOS/360 (Tape Operating System/360 was an IBM Operating system for the System/360, used in the early days around 1965 to support the IBM The IBM Time Sharing System TSS/360 was an early Time-sharing Operating system which ran on a special model of the System/360 line of mainframes the MUSIC/SP (Multi-User System for Interactive Computing / System Product originally "McGill University System for Interactive Computing" was developed at McGill University Michigan Terminal System ( MTS) is an Operating system for the IBM System/360 and its successors that was developed jointly by the following institutions Disk Operating System/360, also DOS/360, or simply DOS, was an Operating system for IBM mainframes It was announced by IBM on the z/VSE (Virtual Storage Extended is an Operating system for IBM mainframe computers the latest one in the DOS/360 lineage, which originated in 1965 See also History of IBM mainframe operating systems OS/360, officially known as IBM System/360 Operating System, was a group of Batch processing In the History of IBM mainframe operating systems, multiprogramming with a fixed number of tasks ( MFT) was one of the three available configurations of the OS/360 Operating System/Virtual Storage 1, or OS/VS1,was an IBM mainframe computer Operating system designed to be run on IBM System/370 Multiple Virtual Storage, more commonly called MVS, was the most commonly used Operating system on the System/370 and System/390 IBM MVS/370 is the earliest currently supported version of the MVS Operating system. MVS/XA, or Multiple Virtual Storage/Extended Architecture, was a version of the IBM operating system that is now called Z/OS. MVS/ESA MVS Enterprise System Architecture Version of MVS, first introduced as MVS/SP Version 3 in February 1988 OS/390 is an IBM Operating system for the System/390 IBM mainframe computers. z/OS is a 64-bit Operating system for Mainframe computers, created by IBM. See also CP/CMS, History of IBM This lengthy article explores the History of CP/CMS — the historical context in which this important IBM Time-sharing CP-40 was a research precursor to CP-67, which in turn was part of IBM's then-revolutionary CP[-67]/CMS &ndash a Virtual machine / Virtual memory CP/CMS was a Time-sharing Operating system of the late 60s and early 70s known for its excellent performance and advanced features See also CP/CMS CP-67 was the control program portion of CP/CMS, a Virtual machine operating system developed for the IBM System/360-67 CP/CMS was a Time-sharing Operating system of the late 60s and early 70s known for its excellent performance and advanced features See also National CSS CP/CMS|History of CP/CMS|IBM System/360-67 VP/CSS was a Time-sharing Operating system developed by National CSS. CP/CMS|History of CP/CMS VM (often VM/CMS) refers to a family of IBM Virtual machine Operating systems used on IBM System/370 CP/CMS|History of CP/CMS VM (often VM/CMS) refers to a family of IBM Virtual machine Operating systems used on IBM System/370 CP/CMS|History of CP/CMS VM (often VM/CMS) refers to a family of IBM Virtual machine Operating systems used on IBM System/370 See also VM (operating system z/VM is the current version in IBM's VM family of Virtual machine Operating systems. IBM Airline Control Program, or ACP, was the Operating system developed by IBM beginning about 1965. TPF is an IBM Real-time operating system for mainframes descended from the IBM System/360 family including ZSeries and System TPF is an IBM Real-time operating system for mainframes descended from the IBM System/360 family including ZSeries and System A Unix-like (sometimes shortened to *nix) Operating system is one that behaves in a manner similar to a Unix system while not necessarily conforming UTS is an implementation of the UNIX Operating system for IBM mainframe (and compatible computers Linux (commonly pronounced ˈlɪnəks IBM mainframes, though perceived as synonymous with Mainframe computers in general due to their marketshare are now technically and specifically IBM 's line of business IBM System z, or earlier IBM eServer zSeries, is a brand name designated by IBM to all its Mainframe computers In 2000 IBM rebranded the existing Other terms with the same meaning include Linux/390, Linux on zSeries, Linux for zSeries, Linux on System z9, zLinux, z/Linux, etc. IBM System z, or earlier IBM eServer zSeries, is a brand name designated by IBM to all its Mainframe computers In 2000 IBM rebranded the existing IBM System z9 is a line of IBM mainframes. It was announced on July 25 2005 and the first models
Contents |
History
Linux on zSeries originated as two separate efforts to port Linux to IBM's largest servers. The first effort, the "Bigfoot" project, developed by Linas Vepstas in late 1998 through early 1999, was an independent distribution and has since been abandoned. IBM published a collection of patches and additions to the Linux 2. 2. 13 kernel on December 18, 1999, to start today's mainline Linux on zSeries. In Computer science, the kernel is the central component of most computer Operating systems (OS Events 218 BC - Second Punic War: Battle of the Trebia - Hannibal 's Carthaginian forces defeat those of the Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Formal product announcements quickly followed in 2000, including the Integrated Facility for Linux (IFL) engines. 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. The Integrated Facility for Linux (IFL is an IBM mainframe processor dedicated to running the Linux operating system with or without z/VM. Think Blue Linux was an early mainframe distribution consisting mainly of Red Hat packages added to the IBM kernel. Think Blue Linux (sometimes ThinkBlue Linux) was a port of Linux to IBM S/390 (later zSeries Mainframe computers done by the Millenux In Computing, Red Hat Inc ( is a company dedicated to Free and open source software, and a major Linux distribution vendor Commercial Linux distributors introduced mainframe editions very quickly after the initial kernel work, and these mainframe versions have now been available for several years.
At the start of IBM's involvement, Linux patches for zSeries included some object code only (OCO) modules, without source code. However, currently Linux on zSeries is completely open source under the GNU General Public License. Open source is a development methodology which offers practical accessibility to a product's source (goods and knowledge This 100% open source status is unusual among Linux distributions, many of which still contain OCO drivers from various vendors who wish to hide proprietary driver implementation details.
Market outlook
Linux is growing rapidly as of mid-2005, and Linux on zSeries is no exception. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. IBM is aggressively promoting Linux on zSeries, and the company is now well-regarded within the Linux community as a defender of open source values, particularly because of its legal battles against the SCO Group. The SCO Group Inc ( TSG, informally SCO;) is a software company formerly called Caldera Systems and Caldera International. In their 2005 "hype" report, IT industry analyst firm Gartner cited Linux on zSeries as arguably the leading driver of Linux's adoption among businesses and governments. Gartner, Inc ( is an information technology research and advisory firm headquartered in Stamford, Connecticut. Quite simply, the expansion of Linux to the mainframe has given Linux as a whole additional market credibility.
IBM announced in May 2006, that over 1,700 customers run Linux on their mainframes — which is a considerable number in the mainframe market.
IBM currently supports two Linux distributions, Red Hat and Novell SuSE. In Computing, Red Hat Inc ( is a company dedicated to Free and open source software, and a major Linux distribution vendor SUSE (ˈsuːsə German ˈzuːzə is a major retail Operating system, produced worldwide and supported by Novell Inc Other notable Linux on zSeries distributions are Debian, Gentoo, Slackware, and CentOS. Debian ( pronounced) is a computer Operating system composed entirely of Free and open source software. The Gentoo Linux Operating system (ˈdʒɛntuː is a Linux distribution based on the Portage Package management system. Slackware is an Operating system created by Patrick Volkerding of Slackware Linux Inc CentOS is a freely-available Operating system that is based on Red Hat Enterprise Linux. The Linux kernel architecture designation is "s390" for 31-bit kernels and "s390x" for 64-bit kernels. Perhaps the only computing architecture based on 31-bit addressing is one of computing's most famous and most profitable '64-bit' CPUs have existed in Supercomputers since the 1960s and in RISC -based workstations and servers since the early 1990s.
Virtualization
Linux is not emulated on a mainframe. An emulator duplicates (provides an emulation of the functions of one System using a different system so that the second system behaves like (and appears to It runs as a complete native operating system, like other mainframe operating systems, at full speed using mainframe processor instructions. Thus, in its simplest configuration, a single instance of Linux can technically occupy a whole mainframe. But this configuration is uncommon and not often economically sensible because IBM System z servers can run mixed workloads, including numerous other operating systems, through the use of virtualization. Both hardware and software co-evolved over decades to support these workloads.
System z mainframes are capable of multiple levels of virtualization. In the first level of virtualization, a single machine can be divided into as many as 60 logical partitions (LPARs), and each LPAR is a separate virtual machine running a separate operating system (OS). LPARs are implemented in hardware using a feature called PR/SM which can (optionally, typically) dynamically adjust LPAR boundaries according to real-time demands. This hardware feature is always active in modern mainframes, even in the simplest configuration with a single LPAR spanning the entire machine.
However, most Linux on System z customers take advantage of an additional virtualization level, z/VM. See also VM (operating system z/VM is the current version in IBM's VM family of Virtual machine Operating systems. This is a mainframe OS with a long history, and one of its main functions is a hypervisor, a provider and manager of virtual machines. Operating systems, such as Linux, that run within a z/VM virtual machine are called guests or images. z/VM virtualizes not only processors and memory but also mainframe (ESCON or FICON) disk storage, networking, cryptographic accelerators, and other mainframe resources. ESCON (Enterprise Systems Connection is a data connection created by IBM, and is commonly used to connect their Mainframe computers to peripheral devices such as FICON ( Fiber Connectivity) is the IBM proprietary name for the ANSI FC-SB-3 Single-Byte Command Code Sets-3 Mapping Protocol for Fibre
z/VM operates inside an LPAR, like any other mainframe OS. This provides two levels of Linux virtualization: based on hardware, and based on a hardware-assisted hypervisor. Moreover, z/VM can also be a guest of z/VM, creating nested levels of virtualization at any number of levels deep. Nested virtualization has little extra overhead and is practical on mainframes.
Hardware
IFLs (Integrated Facility for Linux) are mainframe processors dedicated to running Linux, either natively or under z/VM. The Integrated Facility for Linux (IFL is an IBM mainframe processor dedicated to running the Linux operating system with or without z/VM. Microcode restricts IFLs from running "traditional" workloads, such as z/OS; they are otherwise identical to other zSeries processors. Microprogramming (ie writing microcode) is a method that can be employed to implement Machine instructions in a CPU relatively easily often using less z/OS is a 64-bit Operating system for Mainframe computers, created by IBM. z/OS software vendors do not typically charge for IFL capacity, and IFLs are less expensive than general purpose engines (Central Processors, or CPs). Consequently businesses and governments can easily expand their mainframe Linux installations without affecting most of their software license charges. Although Linux can technically operate on both CPs and IFLs, IFLs simply cost less.
Linux on zSeries is available in both 31-bit and 64-bit versions, with the 64-bit versions rapidly gaining popularity as z/Architecture mainframes become more prevalent than earlier ESA/390 generation. Perhaps the only computing architecture based on 31-bit addressing is one of computing's most famous and most profitable '64-bit' CPUs have existed in Supercomputers since the 1960s and in RISC -based workstations and servers since the early 1990s. z/Architecture, initially called ESA Modal Extensions ( ESAME) refers to IBM 's 64-bit computing architecture for a current generation ESA/390 (Enterprise Systems Architecture/390 was introduced in September 1990 and is IBM 's last 31-bit -address/ 32-bit -data mainframe computing The 64-bit distributions can still run 31-bit applications. The Linux 2. 6. x kernel added substantial support for mainframe hardware, such as ESCON, FICON, SCSI-attached storage devices, and zSeries cryptographic accelerators. ESCON (Enterprise Systems Connection is a data connection created by IBM, and is commonly used to connect their Mainframe computers to peripheral devices such as FICON ( Fiber Connectivity) is the IBM proprietary name for the ANSI FC-SB-3 Single-Byte Command Code Sets-3 Mapping Protocol for Fibre Also several vendor distributions backported 2. Backporting is the action of taking a certain Software modification ( patch) and applying it to an older version of the software than it was initially created for 6. x patches to the Linux 2. 4. x kernel.
Advantages
As one of the most scalable platforms for Linux computing, System z has several major advantages. First, companies and governments can simplify their computing infrastructure. Numerous small Linux and PC servers can be combined onto one mainframe, gaining all the benefits of centralization, but still keeping a multitude of specialized servers thanks to virtualization support, thereby reducing operating costs. File servers, web servers, print servers, name/directory servers, and other "utility" servers are well-suited for that.
Second, Linux on zSeries can take advantage of mainframe qualities of service, especially their reliability and security features, to support continuous business operations. For example, transparent use of redundant processor execution steps and integrity checking. Many industries, including financial services, need this unique capability for their Linux applications. Also, mainframes support "hot" processor replacement. Linux and its applications continue to run, undisturbed, while adding or replacing processors, allowing business-friendly scaling according to demand. Third, IBM's mainframe customers benefit, like other Linux users, from the vast and growing portfolio of useful software applications, including open source innovations.
When Linux applications access mainframe-based data and applications in CICS, IBM DB2, IMS, and other mainframe subsystems, running on the same physical mainframe, they can utilize HiperSockets – fast, memory-only TCP/IP connections. CICS ( Customer Information Control System) is a Transaction server that runs primarily on IBM mainframe systems under Z/OS and Z/VSE DB2 is one of IBM 's families of Relational database management system (RDBMS (or as IBM now calls it data server software products within IBM's broader Information IBM Information Management System ( IMS) is a joint Hierarchical database and Information management system with extensive Transaction processing HiperSocket is an IBM technology for high-speed communications between partitions on a server with a Hypervisor. The Internet Protocol Suite (commonly TCP/IP) is the set of Communications protocols used for the Internet and other similar networks As compared to TCP/IP over standard network interface cards (NICs, in the mainframe world called Open System Adapters, OSAs), HiperSockets can improve end-user responsiveness (reduce network latency and processing overhead), security (since there's no network connection to intercept), and reliability (since there's no network connection to lose). A Network card, Network Adapter, LAN Adapter or NIC (network interface card is a piece of Computer hardware designed to allow computers
z/OS still has numerous reliability and availability advantages over Linux, so most Linux on zSeries customers run both operating systems and will likely do so for the foreseeable future. However, some new, 21st century mainframe buyers run Linux on their systems, some exclusively. It is possible to configure any new mainframe with IFLs only.
Pricing and Costs
A Linux-capable 64-bit mainframe starts at about $40,000 (z800 model 0E1, U.S. early 2008 used system price on Ebay) plus the cost of external disk array plus console and network interconnects. A disk array is a Disk storage system which contains multiple Disk drives It is differentiated from a Disk enclosure, in that an array has Cache Each additional IFL ranges from $95,000 (System z9 BC only) to $125,000, according to IBM's publicly announced list prices as of early 2008. When upgrading a mainframe to a new generation, IBM typically charges a base upgrade fee for the machine hardware but will not charge extra to enable the same number of IFLs that were activated on the prior machine, even though newer models have faster IFLs. This IBM pricing practice is probably unique among servers but has a long history in the mainframe market.
Nonetheless, Linux on System z is not appropriate for small businesses that would have fewer than about 10 distributed Linux servers, although some expensive per-processor licensed software can quickly reduce that rule of thumb. A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation Most software vendors, including IBM, treat the highly virtualized IFLs just like non-virtualized processors on other platforms for licensing purposes. In other words, a single IFL running scores of Linux instances still counts as one "ordinary" CPU, at the same CPU price, for software licensing. Test, development, quality assurance, training, and redundant production server instances can all run on one IFL (or more IFLs, but only if needed for peak demand performance capacity). Thus, beyond some minimum threshold, Linux on System z can quickly become cost-advantageous when factoring in labor and software costs.
The cost equation for Linux on System z is not always well understood and is controversial, and many businesses and governments have difficulty measuring, much less basing decisions on, software, labor, and other costs (such as the costs of outage and security breaches). Acquisition costs are often more visible, and small, non-scalable servers are "cheap. " Nonetheless, non-acquisition costs are no less real and are usually far greater than hardware acquisition prices. Also, individual users and departments within larger businesses and governments sometimes have difficulty sharing computing infrastructure (or any other resources, for that matter), citing a loss of control. Server centralization, as Linux on System z provides, might reward cooperation with better service and lower costs, but that's not to say that cooperation is always easily accomplished within a corporate bureaucracy.
Linux on System z also supports less expensive disk storage devices than z/OS because Linux does not require FICON or ESCON attachment, although z/OS may use disk space more efficiently due to hardware-assisted database compression on z/OS; however this effect is highly variable, and may be eliminated due to the minimum space allocation requirements for z/OS data sets (a full disk track). A data set, or dataset, is a Computer file having a record organization.
Appropriate workloads
Mainframe characteristics are designed for such business workloads as transaction processing or large database management. Mainframe design emphasizes input/output performance, implemented via channel I/O. In Computer science, channel I/O is a generic term that refers to a high-performance Input/output (I/O architecture that is implemented in various forms on a number Historically, the principle is to offload I/O activities from the CPU as much as possible, and the z/Architecture additionally offloads cryptographic calculations. Mainframes can scale to numerous processors in a single frame, i. e. up to 64 processors in the case of the System z10 EC Model E64. IBM System z10 is the latest line of IBM mainframes. It was announced on February 26 2008 and represents the first model powered by the z10 quad core
On the other hand, mainframes in general, and Linux on zSeries in particular, do not perform well, at least on a cost basis, for single task computations. Examples include most scientific simulations, weather forecasting, and molecular modeling. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location Computational chemistry is a branch of Chemistry that uses computers to assist in solving chemical problems Supercomputers, including Linux-based supercomputers, excel at these workloads. A supercomputer is a Computer that is at the frontline of processing capacity particularly speed of calculation (at the time of its introduction This distinction has blurred since the introduction of the System z10, a machine based on quad-core 4. 4 GHz processors with hardware decimal floating point. In this regard, the System z10 more resembles a supercomputer processor than previous mainframes.
Mainframes do not provide any advanced graphics or sound adapters, and are as such ill-suited for digital media editing or computer-aided design (CAD) except perhaps in support roles (e. Digital media (as opposed to analog media) usually refers to Electronic media that work on digital Codes. g. content storage, parts inventories, etc. ).
Support
Like all other versions of Linux, Linux on zSeries is governed by the GPL free software license. Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified Complete Linux on zSeries source code is available from numerous groups on a free and equal basis, and architectural support is now part of the main Linux kernel effort. In Computer science, source code (commonly just source or code) is any sequence of statements or declarations written in some Human-readable IBM assigns several of its programmers to the community effort, but IBM is by no means the only participant.
Most Linux on zSeries customers, particularly those with business-critical production workloads, purchase a software support contract from commercial Linux vendors such as Novell SuSE or Red Hat. IBM Global Services also offers support contracts, including 24x7 coverage. IBM Global Services is the world's largest Business and technology services provider Some standard Linux software applications are readily available pre-compiled, including popular closed-source enterprise software packages such as WebSphere, DB2 and Oracle databases, SAP R/3, and IBM's Java Developer's Kit (JDK). Headline text == WebSphere refers to a Brand of IBM software products that are mostly proprietary, although the term DB2 is one of IBM 's families of Relational database management system (RDBMS (or as IBM now calls it data server software products within IBM's broader Information Oracle Database (commonly referred to as Oracle RDBMS or simply Oracle) is a Relational database management system (RDBMS produced and marketed by SAP R/3 is the former name of the main Enterprise resource planning software produced by SAP AG. Nearly every open source software package available for Linux generally is available for Linux on zSeries, including Apache HTTP Server, Samba software, JBoss, PostgreSQL, MySQL, PHP, Python programming language, Concurrent Versions System, GNU Compiler Collection, and Perl, among many others. Samba is a Free software re-implementation of SMB/CIFS networking protocol, originally developed by Australian Andrew Tridgell JBoss Application Server (or JBoss AS) is a Free software / open source Java EE -based Application server. PostgreSQL is an Object-relational database management system (ORDBMS MySQL is a Relational database management system (RDBMS which has more than 11 million installations PHP is a computer Scripting language. Originally designed for producing Dynamic web pages it has evolved to include a Command line interface capability Python is a general-purpose High-level programming language. Its design philosophy emphasizes programmer productivity and code readability In the field of Software development, the Concurrent Versions System ( CVS) also known as the Concurrent Versioning System, provides a Version The GNU Compiler Collection (usually shortened to GCC) is a set of Compilers produced for various Programming languages by the GNU Project NOTES FOR EDITORS "Perl" is not an acronym (read the "Name" section below
Developer resources
Linux software developers certified for zSeries can appeal to large enterprises and open up additional market opportunity for their products. There are few barriers to doing so as IBM offers a no-charge 30-day Linux on zSeries "test drive", allowing Linux developers of any size access to a live mainframe Linux guest running under z/VM for compiling and testing software. IBM also offers its "Chiphopper" program to help developers write and publish cross-platform Linux software. Siebel, for example, used the Chiphopper program to bring its Java-based CRM software to both Linux on zSeries and z/OS. Siebel, originally Flugzeugbau Halle, was a German Aircraft manufacturer in Halle an der Saale. The official IBM Chiphopper website provides more details about the program. Developers of open source software can make use of a community development system provided by IBM. Open source software (OSS began as a marketing campaign for Free software.
The developer resources can be particularly helpful for performance tuning. Performance tuning is particularly important in mainframe environments with large numbers of users. Mainframe customers tend to expect applications which can scale to high numbers of users and transactions, because that's how they use their systems every day. Sloppy programming is less tolerated, although the mainframe operating environment will keep any such programming from degrading other OS instance's performance. Some Linux application programmers do not expect this exceptional focus on code quality that the mainframe culture and mainframe operating environment demand. However, most developers quickly understand and appreciate this phenomenon, and there's a great deal of professional pride among the growing community of developers with Linux on zSeries experience.
Linux on zSeries supports Unicode and ASCII just like any other Linux distribution—it is not an EBCDIC-based operating system. In Computing, Unicode is an Industry standard allowing Computers to consistently represent and manipulate text expressed in most of the world's American Standard Code for Information Interchange ( ASCII) Extended Binary Coded Decimal Interchange Code ( EBCDIC) is an 8- Bit Character encoding ( Code page) used on IBM mainframe Operating There is nothing inherent in z/Architecture that requires EBCDIC. Even z/OS, for that matter, supports Unicode, ASCII, and EBCDIC. Moving Linux applications to Linux on zSeries almost always involves just simple recompilation of the source code. The few exceptions might include source code which assumes a particular "endian" byte order or inline machine instructions for a specific processor, although these issues are not unique to Linux on zSeries, usually easily remedied, and quite rare.
Although programs can be easily cross compiled to z/Architecture binaries on non-mainframe Linux system, at some point such binary is usually tested either on a real mainframe, or at least on an emulated one. A cross compiler is a Compiler capable of creating Executable code for a platform other than the one on which the compiler is run z/Architecture, initially called ESA Modal Extensions ( ESAME) refers to IBM 's 64-bit computing architecture for a current generation
Emulators
There are at least two software-based zSeries mainframe emulators. An emulator duplicates (provides an emulation of the functions of one System using a different system so that the second system behaves like (and appears to FLEX-ES from Fundamental Software is the officially sanctioned option. The open source Hercules emulator is also available for Linux on zSeries, but not allowed for running any licensed mainframe operating systems, such as z/OS. The Hercules emulator is a computer program which allows software designed for IBM mainframe computers ( System/370, System/390 and ZSeries) to
See also
- Comparison of Linux distributions
- Linux on Power
- OpenSolaris for System z
- UNIX System Services
- zAAP
- z/TPF
- z/VSE
External links
- Linux on System z devel site
- Linux for S/390 and zSeries site
- Linux Technology Center at IBM
- IBM Software for Linux
- IBM Redbook describes the Linux distributions available for the mainframe
- T-Systems Embraces Linux
- IBM Redbook: High Availability Architectures for Linux on System z
- IBM Press Release: Shrinking 3900 Distributed Servers to 30 Linux Mainframes
- Lawson Products: Consolidating on the Mainframe
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