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Encyclopedia > Linux on zSeries

Linux on zSeries (or Linux on System z9) is the preferred collective term for the Linux operating system and GNU/Linux software compiled to run on IBM mainframes, especially zSeries servers. Other terms with the same meaning include Linux/390, Linux for zSeries, and z/Linux. Tux the penguin, based on an image created by Larry Ewing in 1996, is the logo and mascot of Linux. ... An IBM mainframe is a large, high-performance computer made by International Business Machines (IBM). ... Since December, 2001, IBM designates all its mainframes with the name eServer zSeries, with the e depicted in IBMs well-known red trademarked symbol. ...



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. Formal product announcements quickly followed in 2000, including the Integrated Facility for Linux (IFL) engines. Think Blue Linux was another early mainframe distribution, consisting mainly of RedHat packages added to the IBM kernel. International Business Machines Corporation (IBM, or colloquially, Big Blue; NYSE: IBM) is a computer technology firm headquartered in Armonk, NY, USA. The company, which was founded in 1888 and incorporated June 15, 1911, manufactures and sells computer hardware, software, infrastructure services, hosting services, and consulting services. ... In computer science the kernel is the core of an operating system. ... December 18 is the 352nd day of the year (353rd in leap years) in the Gregorian Calendar. ... 1999 (MCMXCIX) was a common year starting on Friday, and was designated the International Year of Older Persons by the United Nations. ... This article is about the year 2000. ... The Integrated Facility for Linux (IFL) is an IBM mainframe processor dedicated to running the Linux operating system, with or without z/VM. IFLs are one of two types of mainframe processors expressly designed to reduce software costs. ... Think Blue Linux (sometimes ThinkBlue Linux) was a port of Linux to IBM S/390 (later, zSeries) mainframe computers, done by the Millenux subsidiary of German company Thinking Objects Software GmbH. The distribution consisted primarily of a collection of Red Hat Linux 6. ...


IBM zSeries/z9 servers can run mixed workloads, including numerous other operating systems, through the use of virtualization technology. Both hardware and software co-evolved over decades to support these workloads, and the Linux OS is no exception. In computing, virtualization is the process of presenting a logical grouping or subset of computing resources so that they can be accessed in ways that give benefits over the original configuration. ...

IFLs (Integrated Facility for Linux) are mainframe processors dedicated to running Linux. Microcode restricts IFLs from running "traditional" workloads, such as z/OS. z/OS software vendors do not typically charge for IFL capacity, and IFLs are less expensive than general purpose engines (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. The Integrated Facility for Linux (IFL) is an IBM mainframe processor dedicated to running the Linux operating system, with or without z/VM. IFLs are one of two types of mainframe processors expressly designed to reduce software costs. ... A microprogram implements a CPU instruction set. ... z/OS Welcome Screen seen through a terminal emulator The title of this article begins with a capital letter due to technical limitations. ...

Linux on zSeries is available in both 31-bit and 64-bit versions, with the 64-bit versions rapidly gaining popularity as zSeries and System z9 mainframes become more prevalent. (The 64-bit distributions can still run 31-bit code.) The Linux 2.6.x kernel added substantial support for mainframe hardware, although several vendor distributions backported 2.6.x patches to the Linux 2.4.x kernel. For example, Linux on zSeries supports ESCON, FICON, SCSI-attached storage devices, and zSeries cryptographic accelerators. ESA/390 (Enterprise Systems Architecture/390) is IBMs 31-bit mainframe computing design, copied by Amdahl, Hitachi, and Fujitsu among other competitors. ... In computing, a 64-bit component is one in which data are processed or stored in 64-bit units (words). ... 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. ... ESCON (or Enterprise Systems Connection) is an optical serial interface between IBM mainframe computers and peripheral devices such as storage and tape drives. ... In computing, FICON (Fiber Connectivity) is an input and output protocol used in IBM mainframe computers and peripheral devices such as storage arrays and tape drives. ... SCSI stands for Small Computer System Interface, and is a standard interface and command set for transferring data between devices on both internal and external computer buses. ...

At the start of IBM's involvement, Linux on zSeries included some OCO (object code only) modules, without source code. However, currently Linux on zSeries is completely open source under the GPL. Open source refers to projects that are open to the public and which draw on other projects that are freely available to the general public. ... The GNU logo Wikisource has original text related to this article: GNU General Public License The GNU General Public License (GNU GPL or simply GPL) is the most popular free software license, originally written by Richard Stallman for the GNU project (GNU itself is a recursive acronym for GNUs...


As one of the most scalable platforms for Linux computing, zSeries/z9 has several major advantages. First, companies and governments can consolidate numerous small Linux and PC servers, retaining the benefits of centralizing, but still keeping a multitude of specialized servers thanks to the virtualization support, thereby reducing operating costs. File servers, Web servers, print servers, name/directory servers, and other "utility" servers are well-suited for consolidation. 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, the zSeries/z9 servers assure that machine instructions execute precisely — 2+2 always equals 4 — using redundant processor execution steps and integrity checking. This execution integrity is automatic and transparent to Linux. 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.

z/OS still has numerous reliability and availability advantages over Linux — even mainframe Linux — so most Linux on zSeries customers run both operating systems and will likely do so for the foreseeable future. However, the majority of new, 21st century mainframe buyers run Linux on their systems, many exclusively. (It is possible to configure any new mainframe with IFLs only.)

Linux on zSeries has unique advantages when Linux applications access mainframe-based data and applications in CICS, DB2, IMS, and other mainframe subsystems. Architecturally, Linux on zSeries enjoys "proximity" to these resources. Linux on zSeries can interact with these resources running on the same physical system using Hipersockets (fast, in-memory TCP/IP connections that reduce network latency and processing overhead). In fact, mainframe customers often discover that their backend mainframe-based subsystems work less hard servicing inbound requests from Linux on zSeries applications than if those applications run "offboard" (on other systems across a physical network). Proximity can improve end-user responsiveness, especially for complex applications which are data-intensive or which require multiple network hops to fulfill application requests. Proximity can also improve security (since there's no network connection to intercept) and reliability (since there's no network connection to lose). CICS® (Customer Information Control System) is a transaction server that runs primarily on IBM mainframe systems under z/OS or z/VSE. CICS is available for other operating systems, notably i5/OS, OS/2, and as the closely related IBM TXSeries software on AIX, Windows, and Linux, among others. ... DB2® is IBMs family of information management software products. ... Information Management System (IMS) is a joint hierarchical database and information management system. ... Hipersocket is an IBM technology for high-speed communications between partitions on a server with a hypervisor. ... The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet runs. ...

Pricing and Costs

A Linux-capable zSeries server starts at "under $200,000" (zSeries 890 Model 110, U.S. 2004 list price, excluding disk storage). Each (additional) IFL costs $125,000 (U.S. 2004 list price) — although the $125,000 is a one-time charge. (Unlike other systems, the only charge for a mainframe upgrade is a "frame charge." Once you pay for a processor you own it through any model upgrades, even though each IFL gets faster with each upgrade. On other systems you pay for processors again with each and every model upgrade.) Thus Linux on zSeries is not appropriate for small businesses with fewer than about 30 Linux servers, although some expensive per-processor licensed software can quickly reduce that "rule of thumb." 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, 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 zSeries can quickly become cost-advantageous when factoring in labor and software costs.

The cost equation for Linux on zSeries 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 consolidation, as Linux on zSeries provides, can reward cooperation with better service and lower costs, but that's not to say that cooperation is always easily accomplished within a corporate bureaucracy. Ultimately market competition will encourage businesses to share infrastructure costs, otherwise they will not be the lowest cost producers.

Linux on zSeries also supports less expensive disk storage devices than z/OS because Linux does not require FICON or ESCON attachment. In computing, FICON (Fiber Connectivity) is an input and output protocol used in IBM mainframe computers and peripheral devices such as storage arrays and tape drives. ... ESCON (or Enterprise Systems Connection) is an optical serial interface between IBM mainframe computers and peripheral devices such as storage and tape drives. ...


zSeries/z9 servers are capable of multiple levels of virtualization (as the hypervisor itself can be virtualized), including LPARs (flexible partitions). Linux on zSeries can occupy whole partitions, even whole servers. However, most Linux on zSeries customers take advantage of z/VM. z/VM provides "virtual machines," with Linux running as a guest operating system under a hypervisor. z/VM dynamically manages processors, memory, and storage on behalf of Linux, carving up a large mainframe into hundreds or even thousands of concurrently operating Linux images. Some other servers support partitions and/or virtual machines, but the zSeries/z9 leads in its scope, scale, and flexibility for Linux computing. A hypervisor in computing is a scheme which allows multiple operating systems to run, unmodified, on a host computer at the same time. ... In IBM mainframe computing, a Logical Partition, commonly called an LPAR, is a virtualized computing environment abstracted from all physical devices. ... VM is an early and influential virtual machine operating system from IBM, apparently the first true virtual machine system. ...

Since the Linux kernel tends to assume that it is the sole OS running, that it "owns" the entire system, including all its memory, z/VM helps "tame" Linux. It is likely that, over time, the Linux kernel will more closely cooperate with z/VM (and vice versa), to better manage memory use in order to further increase capacity. That improvement process has already begun, and z/VM 5.2 introduced many Linux-specific optimizations.

Appropriate Workloads

zSeries/z9 server design emphasizes "balanced" performance, which is to say that the servers have tremendous input/output and memory performance relative to other servers. The zSeries/z9 architecture also emphasizes qualities of service (reliability, availability, security, integrity, etc.) Sheer number-crunching performance is only similar to other servers. However, mainframe philosophy is to keep all the processors "well fed," meaning that mainframe processors typically run at 90% or more utilization round the clock, and they gracefully handle sustained 100% utilization, simply queuing up work in priority order. Cache and memory sizes (and performance) are huge, permitting rapid context switching and large, mixed workloads in a highly virtualized environment. Specialized offload processors for I/O, cryptography, and other purposes make sure that the main processors spend as little effort as possible except on core processing. Mainframes can scale up to huge numbers of processors in a single frame and beyond (in clusters) with near linear scalability. z/VM helps Linux achieve that feat, even up to the 54-way System z9-109 Model S54. These system attributes work well for typical business workloads, especially including transaction processing and large database management.

On the other hand, mainframes (and Linux on zSeries) do not perform well, at least on a cost basis, for workloads that emphasize single task computation. Examples include weather modeling, protein folding analysis, nuclear explosion simulations, digital cinematography, and structural engineering analysis. Supercomputers, including Linux-based supercomputers, excel at these workloads. A supercomputer is a device for turning compute-bound problems into I/O-bound problems. ...


Like all other versions of Linux, Linux on zSeries is governed by the GPL free software license. 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. IBM assigns several of its programmers to the community effort, but IBM is by no means the only participant. This article is about Free Software as defined by the sociopolitical Free Software movement; for information on software distributed without charge, see freeware. ... Source code (commonly just source or code) is any series of statements written in some human-readable computer programming language. ...

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. Most standard Linux software applications are readily available for Linux on zSeries, including popular enterprise software packages such as WebSphere, DB2 and Oracle databases, SAP R/3, and IBM's Java Developer's Kit (JDK). Nearly every open source software package available for Linux 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. SUSE (properly pronounced , but often pronounced /suzi/) is a major retail Linux distribution, produced in Germany. ... Red Hat, Inc. ... IBM Global Services is the worlds largest business and technology services provider. ... WebSphere refers to a brand of IBM software products, although the term also popularly refers to one specific product: WebSphere Application Server (WAS). ... DB2® is IBMs family of information management software products. ... oracle, see Oracle (disambiguation) An Oracle database, strictly speaking, consists of a collection of data managed by an Oracle database management system or DBMS. The term Oracle database sometimes refers — imprecisely — to the DBMS software itself. ... SAP R/3 is the former name of the main ERP software produced by SAP. Its new name is mySAP ERP. // History of SAP R/3 SAP R/2 was a mainframe based business application software suite that was very successful in the 1980s and early 1990s. ... Java is an object-oriented programming language developed by James Gosling and colleagues at Sun Microsystems in the early 1990s. ... Apache HTTP Server is a free software/open source HTTP web server for Unix-like systems (BSD, Linux, and UNIX systems), Microsoft Windows, Novell NetWare and other platforms. ... Samba logo. ... To meet Wikipedias quality standards and conform with our NPOV policy, this article or section may require cleanup. ... PostgreSQL is a free object-relational database server (database management system), released under a flexible BSD-style license. ... David Axmark (left) and Michael Monty Widenius, Founders of MySQL AB, at a conference MySQL is a multithreaded, multi-user, SQL Database Management System (DBMS) with an estimated six million installations. ... PHP is a scripted programming language that can be used to create websites. ... Python is an interpreted programming language created by Guido van Rossum in 1990. ... The Concurrent Versions System (CVS), also known as the Concurrent Versioning System, implements a version control system: it keeps track of all work and all changes in a set of files, typically the implementation of a software project, and allows several (potentially widely separated) developers to collaborate. ... The GNU Compiler Collection (usually shortened to GCC) is a set of programming language compilers produced by the GNU Project. ... Perl, also Practical Extraction and Report Language (a backronym, see below) is a dynamic procedural programming language designed by Larry Wall and first released in 1987. ...

Market outlook

Linux is growing rapidly as of mid-2005, and Linux on zSeries is no exception. As businesses and governments grow their Linux-based computing infrastructures, large zSeries/z9 servers are more popular for consolidation, total cost reduction, and demanding qualities of service (QoS) needs. 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. 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. Quite simply, the expansion of Linux to the mainframe has given Linux as a whole additional market credibility. 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... The SCO Group, Inc. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... Gartner logotype. ...

Novell SuSE currently has the most popular Linux on zSeries distribution, although Red Hat is close behind. Debian, Gentoo, Slackware, and CentOS are other notable Linux on zSeries distributions, although IBM generally recommends Novell and Red Hat distributions. Linux on zSeries distributions start with the mainline "s390" architecture branch of the Linux kernel. SUSE (properly pronounced , but often pronounced /suzi/) is a major retail Linux distribution, produced in Germany. ... Red Hat, Inc. ... It has been suggested that Embedded Debian be merged into this article or section. ... Gentoo Linux is a Linux distribution named after the Gentoo Penguin. ... Slackware was one of the earliest Linux distributions, and is the oldest distribution still being maintained. ... CentOS is a freely available Linux distribution which is based on Red Hats commercial Red Hat Enterprise Linux product, and with which it aims to be 100% compatible. ...

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. See also: Siebel Systems Siebel, originally Flugzeugbau Halle, was a German aircraft manufacturer. ...

There are at least two software-based mainframe emulation packages that can execute zSeries software, including Linux on zSeries. FLEX-ES from Fundamental Software is the officially sanctioned option. Hercules is also available but is not sanctioned for running licensed mainframe operating systems, such as z/OS. An emulator reproducing a console games playable atmosphere on a Windows computer. ... The Hercules emulator is an emulator for the IBM mainframe hardware: the System/370, System/390 and zSeries computers. ...

Linux's design makes it relatively easy to compile applications for multiple platforms. However, the developer resources can be particularly helpful for performance tuning. Performance tuning is particularly important in mainframe environments with large numbers of users.

See also

Linux distributions differ in several important aspects. ... Introduction Linux on eServer p5 series, formerly called RS/6000 (for RISC System/6000), is a ppc64 linux port running on IBM POWER based servers. ... Unix System Services (USS) is a component of z/OS. USS is an adequate, certified Unix implementation (XPG4 UNIX 95). ... zAAP is the zSeries Application Assist Processor, a mainframe processor introduced by IBM in 2004. ... // Overview TPF is an IBM real-time operating system for mainframes descended from the IBM System/360 family, including zSeries and System z9. ... VSE (Virtual Storage Extended) is an operating system for IBM mainframe computers. ...

External links

  • Baldor Electric Consolidates Global Implementation of SAP
  • Lawson Products: Consolidating on the Mainframe
  • Linux Technology Center at IBM
  • IBM Software for Linux
  • Deutsche Bahn (German Rail) Replaces 300 Intel Servers with One Mainframe
  • T-Systems Embraces Linux
  • IBM Redbook describes the Linux distributions available for the mainframe

  Results from FactBites:
IBM developerWorks : Linux : Linux on System z (453 words)
Linux is an operating system whose kernel was developed by Linus Torvalds and initially distributed in 1991.
Linux for S/390® and zSeries® is a port of Linux to the S/390 and zSeries architecture.
Linux for S/390 and zSeries is a "pure" Linux from a user point of view.
Linux/VM: Two great operating systems, even better together (2973 words)
Linux for S/390 and zSeries, also known as Linux/390, is the native port of Linux to the S/390 and zSeries hardware platforms.
Adding a route to the z/VM stack to route the request back into the Linux image completed the circle and allowed all the requests to be processed, but is not the optimal solution.
The Linux piece is a single, critical, component of the entire licensing system.
  More results at FactBites »



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