AIX is a series of proprietary Unix operating systems developed and sold by IBM for several of its computer platforms. Released for the IBM RT PC RISC workstation, AIX now supports or has supported a wide variety of hardware platforms, including the IBM RS/6000 series and POWER and PowerPC-based systems, IBM System i, System/370 mainframes, PS/2 personal computers, the Apple Network Server. AIX is based on UNIX System V with 4.3BSD-compatible extensions. It is one of six commercial operating systems that have versions certified to The Open Group's UNIX 03 standard; the AIX family of operating systems debuted in 1986, became the standard operating system for the RS/6000 series on its launch in 1990, is still developed by IBM. It is supported on IBM Power Systems alongside IBM i and Linux. AIX was the first operating system to have a journaling file system, IBM has continuously enhanced the software with features such as processor and network virtualization, dynamic hardware resource allocation, reliability engineering ported from its mainframe designs.
Unix started life at AT&T's Bell Labs research center in the early 1970s, running on DEC minicomputers. By 1976, the operating system was in use at various academic institutions, including Princeton, where Tom Lyon and others ported it to the S/370, to run as a guest OS under VM/370; this port would grow out to become UTS, a mainframe Unix offering by IBM's competitor Amdahl Corporation. IBM's own involvement in Unix can be dated to 1979, when it assisted Bell Labs in doing its own Unix port to the 370. In the process, IBM made modifications to the TSS/370 hypervisor to better support Unix, it took until 1985 for IBM to offer its own Unix on the S/370 platform, IX/370, developed by Interactive Systems Corporation and intended by IBM to compete with Amdahl UTS. The operating system offered special facilities for interoperating with PC/IX, Interactive/IBM's version of Unix for IBM PC compatible hardware, was licensed at $10,000 per sixteen concurrent users. AIX Version 1, introduced in 1986 for the IBM RT PC workstation, was based on UNIX System V Releases 1 and 2.
In developing AIX, IBM and Interactive Systems Corporation incorporated source code from 4.2 and 4.3 BSD UNIX. Among other variants, IBM produced AIX Version 3, based on System V Release 3, for their POWER-based RS/6000 platform. Since 1990, AIX has served as the primary operating system for the RS/6000 series. AIX Version 4, introduced in 1994, added symmetric multiprocessing with the introduction of the first RS/6000 SMP servers and continued to evolve through the 1990s, culminating with AIX 4.3.3 in 1999. Version 4.1, in a modified form, was the standard operating system for the Apple Network Server systems sold by Apple Computer to complement the Macintosh line. In the late 1990s, under Project Monterey, IBM and the Santa Cruz Operation planned to integrate AIX and UnixWare into a single 32-bit/64-bit multiplatform UNIX with particular emphasis on running on Intel IA-64 architecture CPUs. A beta test version of AIX 5L for IA-64 systems was released, but according to documents released in the SCO v. IBM lawsuit, less than forty licenses for the finished Monterey Unix were sold before the project was terminated in 2002.
In 2003, the SCO Group alleged that IBM had misappropriated licensed source code from UNIX System V Release 4 for incorporation into AIX. IBM maintains that their license was irrevocable, continued to sell and support the product until the litigation was adjudicated. AIX was a component of the 2003 SCO v. IBM lawsuit, in which the SCO Group filed a lawsuit against IBM, alleging IBM contributed SCO's intellectual property to the Linux codebase; the SCO Group, who argued they were the rightful owners of the copyrights covering the Unix operating system, attempted to revoke IBM's license to sell or distribute the AIX operating system. In March 2010, a jury returned a verdict finding that Novell, not the SCO Group, owns the rights to Unix. AIX 6 was announced in May 2007, it ran as an open beta from June 2007 until the general availability of AIX 6.1 on November 9, 2007. Major new features in AIX 6.1 included full role-based access control, workload partitions, enhanced security, Live Partition Mobility on the POWER6 hardware.
AIX 7.1 was announced in April 2010, an open beta ran until general availability of AIX 7.1 in September 2010. Several new features, including better scalability, enhanced clustering and management capabilities were added. AIX 7.1 includes a new built-in clustering capability called Cluster Aware AIX. AIX is able to organize multiple LPARs through the multipath communications channel to neighboring CPUs, enabling high-speed communication between processors; this enables multi-terabyte memory address range and page table access to support global petabyte shared memory space for AIX POWER7 clusters so that software developers can program a cluster as if it were a single system, without using message passing. AIX administrators can use this new capability to cluster a pool of AIX nodes. By default, AIX V7.1 pins kernel memory and includes support to allow applications to pin their kernel stack. Pinning kernel memory and the kernel
Microsoft Windows is a group of several graphical operating system families, all of which are developed and sold by Microsoft. Each family caters to a certain sector of the computing industry. Active Windows families include Windows Embedded. Defunct Windows families include Windows Mobile and Windows Phone. Microsoft introduced an operating environment named Windows on November 20, 1985, as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces. Microsoft Windows came to dominate the world's personal computer market with over 90% market share, overtaking Mac OS, introduced in 1984. Apple came to see Windows as an unfair encroachment on their innovation in GUI development as implemented on products such as the Lisa and Macintosh. On PCs, Windows is still the most popular operating system. However, in 2014, Microsoft admitted losing the majority of the overall operating system market to Android, because of the massive growth in sales of Android smartphones.
In 2014, the number of Windows devices sold was less than 25 %. This comparison however may not be relevant, as the two operating systems traditionally target different platforms. Still, numbers for server use of Windows show one third market share, similar to that for end user use; as of October 2018, the most recent version of Windows for PCs, tablets and embedded devices is Windows 10. The most recent versions for server computers is Windows Server 2019. A specialized version of Windows runs on the Xbox One video game console. Microsoft, the developer of Windows, has registered several trademarks, each of which denote a family of Windows operating systems that target a specific sector of the computing industry; as of 2014, the following Windows families are being developed: Windows NT: Started as a family of operating systems with Windows NT 3.1, an operating system for server computers and workstations. It now consists of three operating system subfamilies that are released at the same time and share the same kernel: Windows: The operating system for mainstream personal computers and smartphones.
The latest version is Windows 10. The main competitor of this family is macOS by Apple for personal computers and Android for mobile devices. Windows Server: The operating system for server computers; the latest version is Windows Server 2019. Unlike its client sibling, it has adopted a strong naming scheme; the main competitor of this family is Linux. Windows PE: A lightweight version of its Windows sibling, meant to operate as a live operating system, used for installing Windows on bare-metal computers, recovery or troubleshooting purposes; the latest version is Windows PE 10. Windows IoT: Initially, Microsoft developed Windows CE as a general-purpose operating system for every device, too resource-limited to be called a full-fledged computer. However, Windows CE was renamed Windows Embedded Compact and was folded under Windows Compact trademark which consists of Windows Embedded Industry, Windows Embedded Professional, Windows Embedded Standard, Windows Embedded Handheld and Windows Embedded Automotive.
The following Windows families are no longer being developed: Windows 9x: An operating system that targeted consumers market. Discontinued because of suboptimal performance. Microsoft now caters to the consumer market with Windows NT. Windows Mobile: The predecessor to Windows Phone, it was a mobile phone operating system; the first version was called Pocket PC 2000. The last version is Windows Mobile 6.5. Windows Phone: An operating system sold only to manufacturers of smartphones; the first version was Windows Phone 7, followed by Windows Phone 8, the last version Windows Phone 8.1. It was succeeded by Windows 10 Mobile; the term Windows collectively describes any or all of several generations of Microsoft operating system products. These products are categorized as follows: The history of Windows dates back to 1981, when Microsoft started work on a program called "Interface Manager", it was announced in November 1983 under the name "Windows", but Windows 1.0 was not released until November 1985.
Windows 1.0 was to achieved little popularity. Windows 1.0 is not a complete operating system. The shell of Windows 1.0 is a program known as the MS-DOS Executive. Components included Calculator, Cardfile, Clipboard viewer, Control Panel, Paint, Reversi and Write. Windows 1.0 does not allow overlapping windows. Instead all windows are tiled. Only modal dialog boxes may appear over other windows. Microsoft sold as included Windows Development libraries with the C development environment, which included numerous windows samples. Windows 2.0 was released in December 1987, was more popular than its predecessor. It features several improvements to the user memory management. Windows 2.03 changed the OS from tiled windows to overlapping windows. The result of this change led to Apple Computer filing a suit against Microsoft alleging infringement on Apple's copyrights. Windows 2.0
The Hewlett-Packard Company or Hewlett-Packard was an American multinational information technology company headquartered in Palo Alto, California. It developed and provided a wide variety of hardware components as well as software and related services to consumers, small- and medium-sized businesses and large enterprises, including customers in the government and education sectors; the company was founded in a one-car garage in Palo Alto by Bill Hewlett and David Packard, produced a line of electronic test equipment. HP was the world's leading PC manufacturer from 2007 to Q2 2013, at which time Lenovo ranked ahead of HP. HP specialized in developing and manufacturing computing, data storage, networking hardware, designing software and delivering services. Major product lines included personal computing devices and industry standard servers, related storage devices, networking products, software and a diverse range of printers and other imaging products. HP directly marketed its products to households, small- to medium-sized businesses and enterprises as well as via online distribution, consumer-electronics and office-supply retailers, software partners and major technology vendors.
HP had services and consulting business around its products and partner products. Hewlett-Packard company events included the spin-off of its electronic and bio-analytical measurement instruments part of its business as Agilent Technologies in 1999, its merger with Compaq in 2002, the acquisition of EDS in 2008, which led to combined revenues of $118.4 billion in 2008 and a Fortune 500 ranking of 9 in 2009. In November 2009, HP announced the acquisition of 3Com, with the deal closing on April 12, 2010. On April 28, 2010, HP announced the buyout of Inc. for $1.2 billion. On September 2, 2010, HP won its bidding war for 3PAR with a $33 a share offer, which Dell declined to match. Hewlett-Packard spun off its enterprise products and services business as Hewlett Packard Enterprise on November 1, 2015. Hewlett-Packard held onto the PC and printer businesses, was renamed to HP Inc. Bill Hewlett and David Packard graduated with degrees in electrical engineering from Stanford University in 1935; the company originated in a garage in nearby Palo Alto during a fellowship they had with a past professor, Frederick Terman at Stanford during the Great Depression.
They considered Terman a mentor in forming Hewlett-Packard. In 1938, Packard and Hewlett begin part-time work in a rented garage with an initial capital investment of US$538. In 1939 Hewlett and Packard decided to formalize their partnership, they tossed a coin to decide whether the company they founded would be called Hewlett-Packard or Packard-Hewlett. HP incorporated on August 18, 1947, went public on November 6, 1957. Of the many projects they worked on, their first financially successful product, was a precision audio oscillator, the Model HP200A, their innovation was the use of a small incandescent light bulb as a temperature dependent resistor in a critical portion of the circuit, the negative feedback loop which stabilized the amplitude of the output sinusoidal waveform. This allowed them to sell the Model 200A for $89.40 when competitors were selling less stable oscillators for over $200. The Model 200 series of generators continued production until at least 1972 as the 200AB, still tube-based but improved in design through the years.
One of the company's earliest customers was Walt Disney Productions, which bought eight Model 200B oscillators for use in certifying the Fantasound surround sound systems installed in theaters for the movie Fantasia. They worked on counter-radar technology and artillery shell fuses during World War II, which allowed Packard to be exempt from the draft. HP is recognized as the symbolic founder of Silicon Valley, although it did not investigate semiconductor devices until a few years after the "traitorous eight" had abandoned William Shockley to create Fairchild Semiconductor in 1957. Hewlett-Packard's HP Associates division, established around 1960, developed semiconductor devices for internal use. Instruments and calculators were some of the products using these devices. During the 1960s, HP partnered with Sony and the Yokogawa Electric companies in Japan to develop several high-quality products; the products were not a huge success, as there were high costs in building HP-looking products in Japan.
HP and Yokogawa formed a joint venture in 1963 to market HP products in Japan. HP bought Yokogawa Electric's share of Hewlett-Packard Japan in 1999. HP spun off Dynac, to specialize in digital equipment; the name was picked so that the HP logo "hp" could be turned upside down to be a reverse reflect image of the logo "dy" of the new company. Dynac changed to Dymec, was folded back into HP in 1959. HP experimented with using Digital Equipment Corporation minicomputers with its instruments, but after deciding that it would be easier to build another small design team than deal with DEC, HP entered the computer market in 1966 with the HP 2100 / HP 1000 series of minicomputers; these had a simple accumulator-based design, with two accumulator registers and, in the HP 1000 models, two index registers. The series was produced for 20 years, in spite of several attempts to replace it, was a forerunner of the HP 9800 and HP 250 series of desktop and business computers; the HP 3000 was an advanced stack-based design for a business computing server redesigned with RISC technology.
The HP 2640 series of smart and intelligent terminals introduced forms-based interfaces to ASCII terminals, introduced screen labeled functio
HP-UX is Hewlett Packard Enterprise's proprietary implementation of the Unix operating system, based on UNIX System V and first released in 1984. Recent versions support the HP 9000 series of computer systems, based on the PA-RISC instruction set architecture, HP Integrity systems, based on Intel's Itanium architecture. Earlier versions of HP-UX supported the HP Integral PC and HP 9000 Series 200, 300, 400 computer systems based on the Motorola 68000 series of processors, as well as the HP 9000 Series 500 computers based on HP's proprietary FOCUS architecture. HP-UX was the first Unix to offer access control lists for file access permissions as an alternative to the standard Unix permissions system. HP-UX was among the first Unix systems to include a built-in logical volume manager. HP has had a long partnership with Veritas Software, uses VxFS as the primary file system, it is one of six commercial operating systems that have versions certified to The Open Group's UNIX 03 standard. HP-UX 11i offers a common root disk for its clustered file system.
HP Serviceguard is the cluster solution for HP-UX. HP Global Workload Management adjusts workloads to optimize performance, integrates with Instant Capacity on Demand so installed resources can be paid for in 30-minute increments as needed for peak workload demands. HP-UX offers operating system-level virtualization features such as hardware partitions, isolated OS virtual partitions on cell-based servers, HP Integrity Virtual Machines on all Integrity servers. HPVM supports guests running on HP-UX 11i v3 hosts – guests can run Linux, OpenVMS 8.4 or HP-UX. HP supports online VM guest migration, where encryption can secure the guest contents during migration. HP-UX 11i v3 scales as follows: 256 processor cores 8 TB main memory 32 TB maximum file system 16 TB maximum file size 128 million ZB—16 million logical units each up to 8ZB. "HP-UX 11i v3". Retrieved 2017-10-31; the 11i v2 release introduced kernel-based intrusion detection, strong random number generation, stack buffer overflow protection, security partitioning, role-based access management, various open-source security tools.
HP classifies the operating system's security features into three categories: data and identity: Release 6.x introduced the context dependent files feature, a method of allowing a fileserver to serve different configurations and binaries to different client machines in a heterogeneous environment. A directory containing such files had its suid bit set and was made hidden from both ordinary and root processes under normal use; such a scheme was sometimes exploited by intruders to hide malicious data. CDFs and the CDF filesystem were dropped with release 10.0. HP-UX operating systems supports a variety of PA-RISC systems; the 11.0 added support for Integrity-based servers for the transition from PA-RISC to Itanium. HP-UX 11i v1.5 is the first version. On the introduction of HP-UX 11i v2 the operating system supported both of these architectures. HP-UX 11i supports HP Integrity Servers of HP BL server blade family; these servers use the Intel Itanium architecture. HP-UX 11i v2 and 11i v3 support HP's CX series servers.
CX stands for carrier grade and is used for telco industry with -48V DC support and is NEBS certified. Both of these systems are discontinued. HP-UX supports HP's RX series of servers. Prior to the release of HP-UX version 11.11, HP used a decimal version numbering scheme with the first number giving the major release and the number following the decimal showing the minor release. With 11.11, HP made a marketing decision to name their releases 11i followed by a v for the version. The i was intended to indicate the OS is Internet-enabled, but the effective result was a dual version-numbering scheme. 1.0 First release for HP 9000 Series 500. HP-UX for Series 500 was different that HP-UX for any other HP machines, as it was layered atop a Series 500 specific operating system called SUNOS. 1.0 AT&T System III based. Support for the HP Integral PC; the kernel runs from ROM. 2.0 First release for HP's early Motorola 68000-based workstations 5.0 ROM-based AT&T System V for the HP Integral PC. Distinct from a HP-UX 5.x for Series 200/300.
3.x HP 9000 Series 600/800 only. Note: 2.x/3.x were developed in parallel with 5.x/6.x, so, for example, 3.x was contemporary with 6.x. The two lines were united at HP-UX 7.x. 6.x Support for HP 9000 Series 300 only. Introduced sockets from 4.3BSD. This version introduced the above-discussed context dependent files, which were removed in release 10 because of their security risks. 7.x Support for HP 9000 Series 300/400, 600/700 /800 HP systems. Provided OSF/Motif. 8.x Support for HP 9000 Series 300/400 600/700/800 systems. Shared libraries introduced. 9.x 9.00, 9.02, 9.04, 9.01, 9.03, 9.05, 9.07, 9.08, 9.09, 9.09+, 9.10. These provided support for the HP 9000 800 systems. Introduced System Administration Manager; the Logical Volume Manager was presented in 9.00 for the Series 800. 10.0 This major release saw a convergence of the operating system between the HP 9000 Series 700 and Series 800 systems, dropping suppor
Computer-aided design is the use of computers to aid in the creation, analysis, or optimization of a design. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, to create a database for manufacturing. CAD output is in the form of electronic files for print, machining, or other manufacturing operations; the term CADD is used. Its use in designing electronic systems is known as electronic design automation. In mechanical design it is known as mechanical design automation or computer-aided drafting, which includes the process of creating a technical drawing with the use of computer software. CAD software for mechanical design uses either vector-based graphics to depict the objects of traditional drafting, or may produce raster graphics showing the overall appearance of designed objects. However, it involves more than just shapes; as in the manual drafting of technical and engineering drawings, the output of CAD must convey information, such as materials, processes and tolerances, according to application-specific conventions.
CAD may be used to design figures in two-dimensional space. CAD is an important industrial art extensively used in many applications, including automotive and aerospace industries and architectural design and many more. CAD is widely used to produce computer animation for special effects in movies and technical manuals called DCC digital content creation; the modern ubiquity and power of computers means that perfume bottles and shampoo dispensers are designed using techniques unheard of by engineers of the 1960s. Because of its enormous economic importance, CAD has been a major driving force for research in computational geometry, computer graphics, discrete differential geometry; the design of geometric models for object shapes, in particular, is called computer-aided geometric design. Starting around the mid 1960s, with the IBM Drafting System, computer-aided design systems began to provide more capability than just an ability to reproduce manual drafting with electronic drafting, the cost-benefit for companies to switch to CAD became apparent.
The benefits of CAD systems over manual drafting are the capabilities one takes for granted from computer systems today. CAD provided the designer with the ability to perform engineering calculations. During this transition, calculations were still performed either by hand or by those individuals who could run computer programs. CAD was a revolutionary change in the engineering industry, where draftsmen and engineering roles begin to merge, it did not eliminate departments, as much as it merged departments and empowered draftsman and engineers. CAD is an example of the pervasive effect. Current computer-aided design software packages range from 2D vector-based drafting systems to 3D solid and surface modelers. Modern CAD packages can frequently allow rotations in three dimensions, allowing viewing of a designed object from any desired angle from the inside looking out; some CAD software is capable of dynamic mathematical modeling. CAD technology is used in the design of tools and machinery and in the drafting and design of all types of buildings, from small residential types to the largest commercial and industrial structures.
CAD is used for detailed engineering of 3D models or 2D drawings of physical components, but it is used throughout the engineering process from conceptual design and layout of products, through strength and dynamic analysis of assemblies to definition of manufacturing methods of components. It can be used to design objects such as jewelry, appliances, etc. Furthermore, many CAD applications now offer advanced rendering and animation capabilities so engineers can better visualize their product designs. 4D BIM is a type of virtual construction engineering simulation incorporating time or schedule related information for project management. CAD has become an important technology within the scope of computer-aided technologies, with benefits such as lower product development costs and a shortened design cycle. CAD enables designers to layout and develop work on screen, print it out and save it for future editing, saving time on their drawings. Computer-aided design is one of the many tools used by engineers and designers and is used in many ways depending on the profession of the user and the type of software in question.
CAD is one part of the whole digital product development activity within the product lifecycle management processes, as such is used together with other tools, which are either integrated modules or stand-alone products, such as: Computer-aided engineering and finite element analysis Computer-aided manufacturing including instructions to computer numerical control machines Photorealistic rendering and motion simulation. Document management and revision control using product data management. CAD is used for the accurate creation of photo simulations that are required in the preparation of environmental impact reports, in which computer-aided designs of intended buildings are superimposed into photographs of existing environments to represent what that locale will be like, where the proposed facilities are allowed to be built. Pote
Computer-aided technologies is the use of computer technology to aid in the design and manufacture of products. Advanced CAx tools merge many different aspects of the product lifecycle management, including design, finite element analysis, production planning, product Computer-aided design Computer-aided architectural design Computer-aided engineering Computer-aided fixture design Computer-aided innovation Computer-aided industrial design Computer-aided manufacturing Computer-aided process planning Computer-aided requirements capture Computer-aided rule definition Computer-aided rule execution Computer-aided software engineering Computer-aided automation Computer-assisted surgery Computer-aided surgical simulation Computational fluid dynamics Component information system Computer-integrated manufacturing Computer Numerical Controlled Electronic design automation Enterprise resource planning Finite element analysis Knowledge-based engineering Manufacturing process management Manufacturing process planning Material requirements planning Manufacturing resource planning Product data management Product lifecycle management Virtual prototyping List of CAx companies LearnCAx Online Education in CAx Technologies
Mainframe computers or mainframes are computers used by large organizations for critical applications. They are larger and have more processing power than some other classes of computers: minicomputers, servers and personal computers; the term referred to the large cabinets called "main frames" that housed the central processing unit and main memory of early computers. The term was used to distinguish high-end commercial machines from less powerful units. Most large-scale computer system architectures were established in the 1960s, but continue to evolve. Mainframe computers are used as servers. Modern mainframe design is characterized less by raw computational speed and more by: Redundant internal engineering resulting in high reliability and security Extensive input-output facilities with the ability to offload to separate engines Strict backward compatibility with older software High hardware and computational utilization rates through virtualization to support massive throughput. Hot-swapping of hardware, such as processors and memory.
Their high stability and reliability enable these machines to run uninterrupted for long periods of time, with mean time between failures measured in decades. Mainframes have high availability, one of the primary reasons for their longevity, since they are used in applications where downtime would be costly or catastrophic; the term reliability and serviceability is a defining characteristic of mainframe computers. Proper planning and implementation is required to realize these features. In addition, mainframes are more secure than other computer types: the NIST vulnerabilities database, US-CERT, rates traditional mainframes such as IBM Z, Unisys Dorado and Unisys Libra as among the most secure with vulnerabilities in the low single digits as compared with thousands for Windows, UNIX, Linux. Software upgrades require setting up the operating system or portions thereof, are non-disruptive only when using virtualizing facilities such as IBM z/OS and Parallel Sysplex, or Unisys XPCL, which support workload sharing so that one system can take over another's application while it is being refreshed.
In the late 1950s, mainframes had only a rudimentary interactive interface, used sets of punched cards, paper tape, or magnetic tape to transfer data and programs. They operated in batch mode to support back office functions such as payroll and customer billing, most of which were based on repeated tape-based sorting and merging operations followed by line printing to preprinted continuous stationery; when interactive user terminals were introduced, they were used exclusively for applications rather than program development. Typewriter and Teletype devices were common control consoles for system operators through the early 1970s, although supplanted by keyboard/display devices. By the early 1970s, many mainframes acquired interactive user terminals operating as timesharing computers, supporting hundreds of users along with batch processing. Users gained access through keyboard/typewriter terminals and specialized text terminal CRT displays with integral keyboards, or from personal computers equipped with terminal emulation software.
By the 1980s, many mainframes supported graphic display terminals, terminal emulation, but not graphical user interfaces. This form of end-user computing became obsolete in the 1990s due to the advent of personal computers provided with GUIs. After 2000, modern mainframes or phased out classic "green screen" and color display terminal access for end-users in favour of Web-style user interfaces; the infrastructure requirements were drastically reduced during the mid-1990s, when CMOS mainframe designs replaced the older bipolar technology. IBM claimed that its newer mainframes reduced data center energy costs for power and cooling, reduced physical space requirements compared to server farms. Modern mainframes can run multiple different instances of operating systems at the same time; this technique of virtual machines allows applications to run as if they were on physically distinct computers. In this role, a single mainframe can replace higher-functioning hardware services available to conventional servers.
While mainframes pioneered this capability, virtualization is now available on most families of computer systems, though not always to the same degree or level of sophistication. Mainframes can add or hot swap system capacity without disrupting system function, with specificity and granularity to a level of sophistication not available with most server solutions. Modern mainframes, notably the IBM zSeries, System z9 and System z10 servers, offer two levels of virtualization: logical partitions and virtual machines. Many mainframe customers run two machines: one in their primary data center, one in their backup data center—fully active active, or on standby—in case there is a catastrophe affecting the first building. Test, development and production workload for applications and databases can run on a single machine, except for large demands where the capacity of one machine might be limiting; such a two-mainframe installation can support continuous business service, avoiding both planned and unplanned outages.
In practice many customers use multiple mainframes linked either by Parallel Sysplex and shared DASD, or with shared, geographically dispersed storage provided by EMC