International Business Machines Corporation is an American multinational information technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the Computing-Tabulating-Recording Company and was renamed "International Business Machines" in 1924. IBM produces and sells computer hardware and software, provides hosting and consulting services in areas ranging from mainframe computers to nanotechnology. IBM is a major research organization, holding the record for most U. S. patents generated by a business for 26 consecutive years. Inventions by IBM include the automated teller machine, the floppy disk, the hard disk drive, the magnetic stripe card, the relational database, the SQL programming language, the UPC barcode, dynamic random-access memory; the IBM mainframe, exemplified by the System/360, was the dominant computing platform during the 1960s and 1970s. IBM has continually shifted business operations by focusing on higher-value, more profitable markets.
This includes spinning off printer manufacturer Lexmark in 1991 and the sale of personal computer and x86-based server businesses to Lenovo, acquiring companies such as PwC Consulting, SPSS, The Weather Company, Red Hat. In 2014, IBM announced that it would go "fabless", continuing to design semiconductors, but offloading manufacturing to GlobalFoundries. Nicknamed Big Blue, IBM is one of 30 companies included in the Dow Jones Industrial Average and one of the world's largest employers, with over 380,000 employees, known as "IBMers". At least 70% of IBMers are based outside the United States, the country with the largest number of IBMers is India. IBM employees have been awarded five Nobel Prizes, six Turing Awards, ten National Medals of Technology and five National Medals of Science. In the 1880s, technologies emerged that would form the core of International Business Machines. Julius E. Pitrap patented the computing scale in 1885. On June 16, 1911, their four companies were amalgamated in New York State by Charles Ranlett Flint forming a fifth company, the Computing-Tabulating-Recording Company based in Endicott, New York.
The five companies had offices and plants in Endicott and Binghamton, New York. C.. They manufactured machinery for sale and lease, ranging from commercial scales and industrial time recorders and cheese slicers, to tabulators and punched cards. Thomas J. Watson, Sr. fired from the National Cash Register Company by John Henry Patterson, called on Flint and, in 1914, was offered a position at CTR. Watson joined CTR as General Manager 11 months was made President when court cases relating to his time at NCR were resolved. Having learned Patterson's pioneering business practices, Watson proceeded to put the stamp of NCR onto CTR's companies, he implemented sales conventions, "generous sales incentives, a focus on customer service, an insistence on well-groomed, dark-suited salesmen and had an evangelical fervor for instilling company pride and loyalty in every worker". His favorite slogan, "THINK", became a mantra for each company's employees. During Watson's first four years, revenues reached $9 million and the company's operations expanded to Europe, South America and Australia.
Watson never liked the clumsy hyphenated name "Computing-Tabulating-Recording Company" and on February 14, 1924 chose to replace it with the more expansive title "International Business Machines". By 1933 most of the subsidiaries had been merged into one company, IBM. In 1937, IBM's tabulating equipment enabled organizations to process unprecedented amounts of data, its clients including the U. S. Government, during its first effort to maintain the employment records for 26 million people pursuant to the Social Security Act, the tracking of persecuted groups by Hitler's Third Reich through the German subsidiary Dehomag. In 1949, Thomas Watson, Sr. created IBM World Trade Corporation, a subsidiary of IBM focused on foreign operations. In 1952, he stepped down after 40 years at the company helm, his son Thomas Watson, Jr. was named president. In 1956, the company demonstrated the first practical example of artificial intelligence when Arthur L. Samuel of IBM's Poughkeepsie, New York, laboratory programmed an IBM 704 not to play checkers but "learn" from its own experience.
In 1957, the FORTRAN scientific programming language was developed. In 1961, IBM developed the SABRE reservation system for American Airlines and introduced the successful Selectric typewriter. In 1963, IBM employees and computers helped. A year it moved its corporate headquarters from New York City to Armonk, New York; the latter half of the 1960s saw IBM continue its support of space exploration, participating in the 1965 Gemini flights, 1966 Saturn flights and 1969 lunar mission. On April 7, 1964, IBM announced the first computer system family, the IBM System/360, it spanned the complete range of commercial and scientific applications from large to small, allowing companies for the first time to upgrade to models with greater computing capability without having to rewrite their applications. It was followed by the IBM System/370 in 1970. Together the
ESCON is a data connection created by IBM, is used to connect their mainframe computers to peripheral devices such as disk storage and tape drives. ESCON is an optical fiber, serial interface, it operated at a rate of 10 Mbyte/s, increased to 17Mbyte/s. The current maximum distance is 43 kilometers. ESCON was introduced by IBM in the early 1990s, it replaced the older, copper-based, parallel, IBM System/360 Bus and Tag channels technology of 1960-1990 era mainframes. Optical fiber is smaller in diameter and weight, hence could save installation costs. Space and labor could be reduced when fewer physical links were required - due to ESCON's switching features. ESCON is being supplanted by the faster FICON, which runs over Fibre Channel. ESCON allows the establishment and reconfiguration of channel connections dynamically, without having to take equipment off-line and manually move the cables. ESCON supports channel connections using serial transmission over a pair of fibers; the ESCON Director supports dynamic switching.
It allows the distance between units to be extended up to 60 km over a dedicated fiber. “Permanent virtual circuits” are supported through the switch. ESCON switching has advantages over a collection of point-to-point links. A peripheral capable of accessing a single mainframe can now be connected to up to eight mainframes, providing peripheral sharing; the ESCON interface specifications were adopted in 1996 by ANSI X3T1 committee as the SBCON standard, now managed by X3T11. Direct access storage device Most important DASD with ESCON interfaces: EMC Symmetrix, DMX and VMAX families. Hewlett Packard Enterprise XP Storage family. Hitachi Data Systems Lightning IBM Enterprise Storage Server IBM Storage DS8000 Sun StorageTek SVA
An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may include accounting software for cost allocation of processor time, mass storage and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is executed directly by the hardware and makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer – from cellular phones and video game consoles to web servers and supercomputers; the dominant desktop operating system is Microsoft Windows with a market share of around 82.74%. MacOS by Apple Inc. is in second place, the varieties of Linux are collectively in third place. In the mobile sector, use in 2017 is up to 70% of Google's Android and according to third quarter 2016 data, Android on smartphones is dominant with 87.5 percent and a growth rate 10.3 percent per year, followed by Apple's iOS with 12.1 percent and a per year decrease in market share of 5.2 percent, while other operating systems amount to just 0.3 percent.
Linux distributions are dominant in supercomputing sectors. Other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can only run one program at a time, while a multi-tasking operating system allows more than one program to be running in concurrency; this is achieved by time-sharing, where the available processor time is divided between multiple processes. These processes are each interrupted in time slices by a task-scheduling subsystem of the operating system. Multi-tasking may be characterized in co-operative types. In preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, such as Solaris and Linux—as well as non-Unix-like, such as AmigaOS—support preemptive multitasking. Cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking.
32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem. A multi-user operating system extends the basic concept of multi-tasking with facilities that identify processes and resources, such as disk space, belonging to multiple users, the system permits multiple users to interact with the system at the same time. Time-sharing operating systems schedule tasks for efficient use of the system and may include accounting software for cost allocation of processor time, mass storage and other resources to multiple users. A distributed operating system manages a group of distinct computers and makes them appear to be a single computer; the development of networked computers that could be linked and communicate with each other gave rise to distributed computing. Distributed computations are carried out on more than one machine; when computers in a group work in cooperation, they form a distributed system.
In an OS, distributed and cloud computing context, templating refers to creating a single virtual machine image as a guest operating system saving it as a tool for multiple running virtual machines. The technique is used both in virtualization and cloud computing management, is common in large server warehouses. Embedded operating systems are designed to be used in embedded computer systems, they are designed to operate on small machines like PDAs with less autonomy. They are able to operate with a limited number of resources, they are compact and efficient by design. Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is an operating system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, it uses specialized scheduling algorithms so that a deterministic nature of behavior is achieved. An event-driven system switches between tasks based on their priorities or external events while time-sharing operating systems switch tasks based on clock interrupts.
A library operating system is one in which the services that a typical operating system provides, such as networking, are provided in the form of libraries and composed with the application and configuration code to construct a unikernel: a specialized, single address space, machine image that can be deployed to cloud or embedded environments. Early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could automatically run different programs in succession to speed up processing. Operating systems did not exist in their more complex forms until the early 1960s. Hardware features were added, that enabled use of runtime libraries and parallel processing; when personal computers became popular in the 1980s, operating systems were made for them similar in concept to those used on larger computers. In the 1940s, the earliest electronic digital systems had no operating systems.
Electronic systems of this time were programmed on rows of mechanical switches or by jumper wires on plug boards. These were special-purpose systems that, for example, generated ballistics tables for the military or controlled the pri
IBM mainframes are large computer systems produced by IBM since 1952. During the 1960s and 1970s, IBM dominated the large computer market. Current mainframe computer in IBM's line of business computers are developments of the basic design of the IBM System/360. From 1952 into the late 1960s, IBM manufactured and marketed several large computer models, known as the IBM 700/7000 series; the first-generation 700s were based on vacuum tubes, while the second-generation 7000s used transistors. These machines established IBM's dominance in electronic data processing. IBM had two model categories: one for engineering and scientific use, one for commercial or data processing use; the two categories and commercial used common peripherals but had different instruction sets, there were incompatibilities within each category. IBM sold its computers without any software, expecting customers to write their own. IBM provided compilers for the newly developed higher-level programming languages Fortran, COMTRAN and COBOL.
The first operating systems for IBM computers were written by IBM customers who did not wish to have their expensive machines sitting idle while operators set up jobs manually. These first operating systems were scheduled work queues, it is thought that the first operating system used for real work was GM-NAA I/O, produced by General Motors' Research division in 1956. IBM enhanced one of GM-NAA I/O's successors, the SHARE Operating System, provided it to customers under the name IBSYS; as software became more complex and important, the cost of supporting it on so many different designs became burdensome, this was one of the factors which led IBM to develop System/360 and its operating systems. The second generation products were a mainstay of IBM's business and IBM continued to make them for several years after the introduction of the System/360. Prior to System/360, IBM sold computers smaller in scale that were not considered mainframes, though they were still bulky and expensive by modern standards.
These included: IBM 650 IBM 305 RAMAC IBM 1400 series IBM 1620 IBM had difficulty getting customers to upgrade from the smaller machines to the mainframes because so much software had to be rewritten. The 7010 was introduced in 1962 as a mainframe-sized 1410; the Systems 360 and 370 could emulate the 1400 machines. A desk-size machine with a different instruction set, the IBM 1130, was released concurrently with the System/360 to address the niche occupied by the 1620, it used the same EBCDIC character encoding as the 360 and was programmed in Fortran, easy to adapt to larger machines when necessary. Midrange computer is a designation used by IBM for a class of computer systems which fall in between mainframes and microcomputers. All that changed with the announcement of the System/360 in April, 1964; the System/360 was a single series of compatible models for both commercial and scientific use. The number "360" suggested a "360 degree," or "all-around" computer system. System/360 incorporated features, present on only either the commercial line or the engineering and scientific line.
Some of the arithmetic units and addressing features were optional on some models of the System/360. However, models were upward compatible and most were downward compatible; the System/360 was the first computer in wide use to include dedicated hardware provisions for the use of operating systems. Among these were supervisor and application mode programs and instructions, as well as built-in memory protection facilities. Hardware memory protection was provided to protect the operating system from the user programs and user tasks from each other; the new machine had a larger address space than the older mainframes, 24 bits addressing 8-bit bytes vs. a typical 18 bits addressing 36-bit words. The smaller models in the System/360 line were intended to replace the 1400 series while providing an easier upgrade path to the larger 360s. To smooth the transition from the second generation to the new line, IBM used the 360's microprogramming capability to emulate the more popular older models, thus 360/30s with this added cost feature could run 1401 programs and the larger 360/65s could run 7094 programs.
To run old programs, the 360 had to be restarted in emulation mode. Many customers kept using their old software and one of the features of the System/370 was the ability to switch to emulation mode and back under operating system control. Operating systems for the System/360 family included OS/360, BOS/360, TOS/360, DOS/360; the System/360 evolved into the System/370, the System/390, the 64-bit zSeries, System z, zEnterprise machines. System/370 introduced virtual memory capabilities in all models other than the first System/370 models.
Z/OS is a 64-bit operating system for IBM mainframes, produced by IBM. It is the successor to OS/390, which in turn followed a string of MVS versions. Like OS/390, z/OS combines a number of separate, related products, some of which are still optional. Z/OS offers the attributes of modern operating systems but retains much of the functionality originating in the 1960s and each subsequent decade, still found in daily use. Z/OS was first introduced in October 2000. Z/OS supports stable mainframe systems and standards such as CICS, COBOL, IMS, DB2, RACF, SNA, IBM MQ, record-oriented data access methods, REXX, CLIST, SMP/E, JCL, TSO/E, ISPF, among others. However, z/OS supports 64-bit Java, C, C++, UNIX APIs and applications through UNIX System Services – The Open Group certifies z/OS as a compliant UNIX operating system – with UNIX/Linux-style hierarchical HFS and zFS file systems; as a result, z/OS hosts a broad range of open source software. Z/OS can communicate directly via TCP/IP, including IPv6, includes standard HTTP servers along with other common services such as FTP, NFS, CIFS/SMB.
Another central design philosophy is support for high quality of service within a single operating system instance, although z/OS has built-in support for Parallel Sysplex clustering. Z/OS has a Workload Manager and dispatcher which automatically manages numerous concurrently hosted units of work running in separate key-protected address spaces according to dynamically adjustable goals; this capability inherently supports multi-tenancy within a single operating system image. However, modern IBM mainframes offer two additional levels of virtualization: LPARs and z/VM; these new functions within the hardware, z/OS, z/VM — and Linux and OpenSolaris support — have encouraged development of new applications for mainframes. Many of them utilize the WebSphere Application Server for z/OS middleware. From its inception z/OS has supported tri-modal addressing. Up through Version 1.5, z/OS itself could start in either 31-bit ESA/390 or 64-bit z/Architecture mode, so it could function on older hardware albeit without 64-bit application support on those machines.
IBM support for z/OS 1.5 ended on March 31, 2007. Now z/OS only runs in 64-bit mode. Application programmers can still use any addressing mode: all applications, regardless of their addressing mode, can coexist without modification, IBM maintains commitment to tri-modal backward compatibility. However, increasing numbers of middleware products and applications, such as DB2 Version 8 and above, now require and exploit 64-bit addressing. IBM markets z/OS as its flagship operating system, suited for continuous, high-volume operation with high security and stability. Z/OS is available under standard license pricing as well as via IBM Z New Application License Charges and "IBM Z Solution Edition," two lower priced offerings aimed at supporting newer applications. U. S. standard commercial z/OS pricing starts at about $125 per month, including support, for the smallest zNALC installation running the base z/OS product plus a typical set of optional z/OS features. Z/OS introduced Variable Workload License Charges and Entry Workload License Charges which are sub-capacity billing options.
VWLC and EWLC customers only pay for peak monthly z/OS usage, not for full machine capacity as with the previous OS/390 operating system. VWLC and EWLC are available for most IBM software products running on z/OS, their peaks are separately calculated but can never exceed the z/OS peak. To be eligible for sub-capacity licensing, a z/OS customer must be running in 64-bit mode, must have eliminated OS/390 from the system, must e-mail IBM monthly sub-capacity reports. Sub-capacity billing reduces software charges for most IBM mainframe customers. Advanced Workload License Charges is the successor to VWLC on mainframe models starting with the zEnterprise 196, EAWLC is an option on zEnterprise 114 models. AWLC and EAWLC offer further sub-capacity discounts. Within each address space, z/OS permits the placement of only data, not code, above the 2 GB "bar". Z/OS enforces this distinction for performance reasons. There are no architectural impediments to allowing more than 2 GB of application code per address space.
IBM has started to allow Java code running on z/OS to execute above the 2 GB bar, again for performance reasons. Starting with z/OS version 2 release 3, code may be placed and executed above the 2 GB "bar"; however few z/OS services may be invoked from above the "bar". Memory is obtained as "Large Memory Objects" in multiples of 1 MB. There are three types of large memory objects: Unshared – where only the creating address space can access the memory. Shared – where the creating address space can give access to specific other address spaces. Common – where all address spaces can access the memory. Generation Data Group is a special type of file used by IBM's mainframe operating system z/OS; the actual GDG is a description of how many generations of a file are to be kept and how old the oldest generation must be at least before it is deleted. Whenever a new generation is created, the system checks whether one or more obso
IBM System z9
IBM System z9 is a line of IBM mainframe computers. The first models were available on September 16, 2005; the System z9 marks the end of the used eServer zSeries naming convention. It was the last mainframe computer that NASA used. System z9 is a mainframe using the z/Architecture known as ESAME. Z/Architecture is a 64-bit architecture which replaces the previous 31-bit-addressing/32-bit-data ESA/390 architecture while remaining compatible with it as well as the older 24-bit-addressing/32-bit-data System/360 architecture; the primary advantage of this arrangement is that memory intensive applications like DB2 are no longer bounded by 31-bit memory restrictions while older applications can run without modifications. With the announcement of the System z9 Business Class server, IBM has renamed the System z9 109 as the System z9 Enterprise Class server. IBM documentation abbreviates them as the z9 z9 EC, respectively. There are several functional enhancements in the System z9 compared to its zSeries predecessors.
Some of the differences include: The Support Element is the most direct and lowest level way to access a mainframe. It circumvents the Hardware Management Console and the operating system running on the mainframe; the HMC is a PC emulates the Support Element. All preceding zSeries mainframes used a modified version of OS/2 with custom software to provide the interface. System z9's HMC no longer uses OS/2, but instead uses a modified version of Linux with an OS/2 lookalike interface to ease transition as well as a new interface. Unlike the previous HMC application on OS/2, the new HMC is web-based which means that local access is done via a web browser. Remote HMC access is available; the web-based nature means that there is no longer a difference between local console access and remote access, which means a remote user has full control if authorized, allowing more flexibility for locating systems within data centers. IBM refers to the new HMC as a "closed platform" which does not allow the user to install software or access the command line interface to increase security and stability.
The HMC is firewalled by default with a minimal number of open ports for remote access. Program Directed Re-IPL is a new feature for Linux on System z9, it allows Linux systems running in an LPAR to re-IPL themselves without operator intervention. This is accomplished by the System z9 storing the device and load parameters used to IPL the system. DB2, VSAM, other data storage formats achieve greater I/O performance thanks to a new System z9 feature called a MIDAW; the System z9 introduces the zIIP, a new type of processor that accelerates certain specific DB2 tasks. Java 1.4 and higher support both 32-bit and 64-bit operation on z9. The System z9 supports the zAAP processor, which allows most of the Java workload to be offloaded from the normal instruction processors. Java workloads executed by the zAAP processor do not count towards the IBM-rated capacity of the z9; this reduces the z9's total cost of ownership compared with other IBM platforms, as otherwise IBM would raise a customer's license fees after installing an additional processor.
The zAAP enables integration of new Java based Web applications with core z/OS backend database environment for high performance, reliability and security. The System z9 adds 128-Bit Advanced Encryption Standard to the list of hardware-based cryptographic algorithms. Other hardware-boosted features include additional random number generation and SHA algorithms; this specialized encryption hardware means System z9 outperforms other platforms which must rely on encryption software. The System z9 supports up to 60 LPARs, up from the previous maximum of 30; the System z9 supports twice its immediate predecessors' maximum memory configurations: now up to 512 GB for the z9 EC and up to 64 GB for the z9 BC. The System z9 supports memory replacement; that means a technician can replace an entire system board without ending any applications and without restarting any operating systems. In most configurations a System z9 can manage this feat without any reduction in performance or capacity for the running applications.
In May 2006, IBM added 4 Gigabit FICON and FCP support to the System z9 for faster I/O to storage devices. IBM added a lower cost 2-port 4 Gbit FICON/FCP I/O adapter to the System z9 option list. In May 2006, IBM introduced subcapacity settings to its high end model. For the first time mainframe processors now allow small, smooth steps through the entire processor range; this feature allows IBM's customers to control their software costs and to pay for only as much capacity as they need without harsh price discontinuities at certain capacity increments. Available with z/OS Release 8, Group Capacity Limits allows an installation to define a group of LPARs within a single z9 or z10 machine whose capacity usage can be limited to a specific number of MSUs. Usage is based on the rolling 4 hour average CPU consumption in MSUs. A group need not be the same as an LPAR Cluster. LPARs can participate. While previous mainframe generations supported specialty processors, such as zAAPs and ICFs, these were all managed by PR/SM out of the same processor pool.
The IBM System z9 EC introduced the concept of separ
Linux on z Systems
Linux on IBM Z is the collective term for the Linux operating system compiled to run on IBM mainframes IBM Z and IBM LinuxONE servers. Similar terms which imply the same meaning are Linux on zEnterprise, Linux on zSeries, Linux/390, Linux/390x, etc; the terms zLinux or z/Linux are sometimes used, but these terms are discouraged by IBM as they create the implication of an IBM-offered or IBM-distributed version of Linux, incorrect. Linux on IBM Z 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 Z. Formal product announcements followed in 2000, including the Integrated Facility for Linux engines. Think Blue Linux was an early mainframe distribution consisting of Red Hat packages added to the IBM kernel.
Commercial Linux distributors introduced mainframe editions quickly after the initial kernel work. At the start of IBM's involvement, Linux patches for IBM Z included some object code only modules, without source code. Soon after IBM replaced the OCO modules with open source modules. Linux on z is free software under the GNU General Public License. According to IBM, by May, 2006, over 1,700 customers were running Linux on their mainframes. Virtualization is required by default on IBM Z. First layer virtualization is provided by the Processor Resource and System Manager to deploy one or more Logical Partitions; each LPAR supports a variety of operating systems including Linux on IBM Z. A hypervisor called z/VM can be run as the second layer virtualization in LPARs to create as many virtual machines as there are resources assigned to the LPARs to support them. KVM on z is another hypervisor option; when Linux applications in an LPAR access data and applications in other LPARs such as CICS, IBM DB2, IMS, other mainframe subsystems, running on the same physical mainframe, they can utilize HiperSockets – fast, memory-only TCP/IP connections.
As compared to TCP/IP over standard network interface cards, HiperSockets can improve end-user responsiveness and reliability. With the zEC12, zBC12, models, the HiperSocket concept is extended beyond the physical machine boundary via an RDMA over Converged Ethernet adapter to facilitate a secure and high speed inter-system communication. Applications in LPAR A in system A can thus use HiperSockets to communicate with applications in LPAR B in system B to ensure the security and performance attributes. Beginning with Linux kernel version 4.1 released in early 2015, Linux on z is only available as a 64-bit operating system compatible with z/Architecture mainframes. Linux on z was available as a 31-bit operating system compatible with older model mainframes introduced prior to 2000's z900 model. However, the newer 64-bit Linux kernel and 64-bit Linux on z distributions are still backward compatible with applications compiled for 31-bit Linux on z; the Linux kernel architecture designations were "s390" and "s390x" to distinguish between the 31-bit and 64-bit Linux on z kernels but "s390" now refers to the one Linux on z kernel architecture.
Linux runs on general purpose mainframe CPs as well as IFLs. IFLs are mainframe processors dedicated to running Linux, either natively or under a hypervisor. Microcode restricts IFLs from running "traditional" workloads, such as z/OS, but they are physically identical to other z System processors. IFLs are less expensive to acquire from IBM than CPs. Linux on z gives the flexibility of running Linux with the advantages of fault-tolerant mainframe hardware capable of over 90,000 I/O operations per second and with a mean time between failure measured in decades. Using virtualization, numerous smaller servers can be combined onto one mainframe, gaining some benefits of centralization and cost reduction, while still allowing specialized servers. Instead of paravirtualization, IBM mainframes use full virtualization, which permits workload density far greater than paravirtualization does. Combining full virtualization of the hardware plus lightweight Virtual Machine containers that run Linux in isolation result in a platform that supports more virtual servers than any other in a single footprint, which can lower operating costs.
Additional savings can be seen from reduced need for floor space, cooling, networking hardware, the other infrastructure needed to support a data center. IBM mainframes allow transparent use of redundant processor execution steps and integrity checking, important for critical applications in certain industries such as banking.. Mainframes allow hot-swapping of hardware, such as processors and memory. IBM Z provides fault tolerance for all key components, including processors, memory, I/O Interconnect, power supply, channel