Once application migration is completed, IBM recommends migration to a different operating system, suggesting Linux as an alternative.

The primary operating systems in use on current IBM mainframes include z / OS ( which followed MVS and OS / 390 ), z / VM ( previously VM / CMS ), z / VSE ( which is in the DOS / 360 lineage ), z / TPF ( a successor of Airlines Control Program ), and Linux on System z such as SUSE Linux Enterprise Server and others.

Modern mainframes, notably the IBM zSeries, System z9 and System z10 servers, offer two levels of virtualization: logical partitions ( LPARs, via the PR / SM facility ) and virtual machines ( via the z / VM operating system ).

) In late 2000 IBM introduced 64-bit z / Architecture, acquired numerous software companies such as Cognos and introduced those software products to the mainframe.

For instance, IBM OS / 390, now z / OS, qualifies as a " Unix " despite having no code in common.

It is common for TPF sites to also use other IBM mainframe operating systems, such as z / OS and z / VM, for offline and complementary processing.

IBM announced the delivery of the next release of TPF, dubbed z / TPF V1. 1, in September 2005.

However, C language programming is much easier to obtain skilled people in, so most if not all new development is done in C. Since z / TPF allows assembler programs to be repackaged into 1 logical file, critical legacy applications can be maintained and actually improve efficiency-the cost of entering one of these programs will now come at the initial enter when the entire program is fetched into core and logical flow through the program is accomplished via simple branch instructions, instead of a dozen or so IBM instructions previously needed to perform what is known as ' core resident enter / back '.

* z / TPF ( IBM )

In addition to CMS, in the early stage especially communication tasks were performed by multitasking VMs ( RSCS, GCS, TCP / IP, UNIX ), and users can run any of the other IBM operating systems, such as MVS, even a new CP itself or now z / OS.

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.

IBM released z / VSE Version 4 in 2007. z / VSE Version 4 requires 64-bit z / Architecture hardware and supports 64-bit real mode addressing.

* IBM z / VSE website

The IBM mainframe z / OS operating system / platform has arguably the most highly refined and evolved set of batch processing facilities owing to its origins, long history, and continuing evolution, and today such systems commonly support hundreds or even thousands of concurrent online and batch tasks within a single operating system image.

z / OS is a 64-bit operating system for mainframe computers, produced by IBM.

However, modern IBM mainframes also offer two additional levels of virtualization: LPARs and ( optionally ) z / VM.

The IBM Program Number for all z / OS Version 1 releases is 5694-A01.

* Attached Support Processor, one of the two early IBM System / 360 programs that replaces the native SPOOL facilities of OS / 360 ; the other was Houston Automatic Spooling Priority ( HASP ).

* Auxiliary Storage Pool, a group of disk drives in the IBM i ( aka OS / 400 ) operating system

Originally released for the IBM 6150 RISC workstation, AIX now supports or has supported a wide variety of hardware platforms, including the IBM RS / 6000 series and later IBM POWER and PowerPC-based systems, IBM System i, System / 370 mainframes, PS / 2 personal computers, and the Apple Network Server.

The AIX family of operating systems debuted in 1986, became the standard operating system for the RS / 6000 series on its launch in 1990, and is still actively developed by IBM.

Among other variants, IBM later produced AIX Version 3 ( also known as AIX / 6000 ), based on System V Release 3, for their IBM POWER-based RS / 6000 platform.

Since 1990, AIX has served as the primary operating system for the RS / 6000 series ( later renamed IBM eServer pSeries, then IBM System p, and now IBM Power Systems ).

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 ( Itanium ) architecture CPUs.

The original AIX ( sometimes called AIX / RT ) was developed for the IBM 6150 RT workstation by IBM in conjunction with Interactive Systems Corporation, who had previously ported UNIX System III to the IBM PC for IBM as PC / IX.

* The DOS / 360 initial / simple operating system for the IBM System / 360 family of mainframe computers ( it later became DOS / VSE, and was eventually just called VSE ).

It was developed by IBM, but is unrelated to IBM's other mainframe operating systems, e. g., VSE, VM.

" Newer licensed operating systems, such as OS / 390, z / OS, VSE / ESA, z / VSE, VM / ESA, z / VM, TPF / ESA, and z / TPF are technically compatible but cannot legally run on the Hercules emulator except in very limited circumstances, and they must always be licensed from IBM.

IBM maintained full compatibility with the past, so that programs developed in the sixties can still run under z / VSE ( if developed for DOS / 360 ) or z / OS ( if developed for MFT or MVT ) with no change.

DB2 is also embedded in the i5 / OS operating system for IBM System i ( iSeries, formerly the AS / 400 ), and versions are available for z / VSE and z / VM.

Source code distribution of other IBM operating systems may have continued for some time ( e. g. OS / 360, DOS / 360, DOS / VSE, MVS, and even TSS / 370, which all today are generally considered to be in the public domain ) since they were arguably published without a copyright notice before 1978.

This usage arose because administration of IBM mainframes often involved the writing of custom assembler code ( IBM's Basic Assembly Language-" BAL "), which integrated with the Operating System such as OS / MVS, DOS / VSE or VM / CMS.

There are actually two IBM JCLs: one for the operating system lineage that begins with DOS / 360 and whose latest member is z / VSE ; and the other for the lineage from OS / 360 to z / OS.

Customer Information Control System ( CICS ) is a transaction server that runs primarily on IBM mainframe systems under z / OS and z / VSE.

In May, 2006, IBM announced that the next version of z / VSE, Version 4, would require a 64-bit system, signaling the end to 31-bit support for that operating system.

MSP is most similar to classic IBM MVS / ESA, and XSP is most similar to classic IBM VSE / ESA.

SSX / VSE (" Small System Executive ") was an attempt by IBM to simplify purchase and installation of VSE by providing a pre-generated system containing the OS and the most popular products.

In 1986 IBM released VSE / SP (" System Product ") in conjunction with the announcement of the 9370 processors.

* IBM System z: CICS Transaction Server, IMS, z / OS Batch, UNIX System Services, WebSphere Application Server, z / VSE, Linux

Like IBM, Burroughs tried to supply a complete line of products for its customers, including Burroughs-designed printers, disk drives, tape drives, computer printing paper, and even typewriter ribbons.

However, the PDP-6 proved to be a " hard sell " with customers, as it offered few advantages over similar machines from the better established vendors like IBM or Honeywell, in spite of its low cost around $ 300, 000.

IBM initially sold its computers without any software, expecting customers to write their own ; programs were manually initiated, one at a time.

The first operating systems for IBM computers were written by IBM customers who did not wish to have their very expensive machines ($ 2M USD in the mid-1950s ) sitting idle while operators set up jobs manually.

IBM enhanced one of GM-NAA I / O's successors, the SHARE Operating System, and provided it to customers under the name IBSYS.

IBM had difficulty getting customers to upgrade from the smaller machines to the mainframes because so much software had to be rewritten.

* OS / 2 1. x targeted the 80286 processor: IBM insisted on supporting the Intel 80286 processor, with its 16-bit segmented memory mode, due to commitments made to customers who had purchased many 80286-based PS / 2's because of IBM's promises surrounding OS / 2.

IBM urges customers to migrate their often highly complex applications to e-business technologies such as Java in a platform-neutral manner.

There is a community of OS / 2 users and developers, along with loyal company customers, hoping that IBM will release OS / 2 or a significant part of it as open source.

In addition, SGI had a large number of software customers ; by changing to the OpenGL API they planned to keep their customers locked onto SGI ( and IBM ) hardware for a few years while market support for OpenGL matured.

IBM owned and leased to its customers more than 90 percent of all tabulating machines in the United States at the time.

In 1936 the US Supreme Court upheld a lower court decision that IBM, together with Remington, should cease its practice of requiring its customers to buy their punch cards from it alone.

Sub-capacity billing substantially reduces software charges for most IBM mainframe customers.

For example, IBM customers running Release 9 can upgrade directly to Release 11 ( or Release 10 ), and both releases can operate concurrently within the same Sysplex ( cluster ) and without conflict using the same datasets, configurations, security profiles, etc.

Although z / OS customers vary in their maintenance practices, IBM encourages every z / OS customer to adopt a reasonable preventive maintenance strategy, to avoid known problems before they might occur.

In July, 2009, TurboHercules SAS asked IBM to license z / OS to its customers for use on systems sold by TurboHercules.

Most other early operating systems for IBM mainframes were also produced by customers.

IBM wanted customers to upgrade their 155 and 165 systems to the widely-sold S / 370-158 and-168.

" The upgrade, required to run OS / VS1 or OS / VS2, was not cost effective for most customers by the time IBM could actually deliver and install it, so many customers were stuck with these machines running MVT until their lease ended.

It was not unusual for this to be another four, five or even six years for the more unfortunate ones, and turned out to be a significant factor in the slow adoption of OS / VS2 MVS, not only by customers in general, but for many internal IBM sites as well.

Soon after, Apple, as one of Motorola's largest customers of desktop-class microprocessors, asked Motorola to join the discussions because of their long relationship, their more extensive experience with manufacturing high-volume microprocessors than IBM, and to serve as a second source for the microprocessors.