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.

TPF is also designed for highly reliable, continuous ( 24x7 ) operation.

It is not uncommon for TPF customers to have continuous online availability of a decade or more, even with system and software upgrades.

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.

It is also possible to run a close cousin of TPF, called ALCS, atop z / OS rather than as a separate operating system.

TPF is capable of running on a multiprocessor, that is, on mainframe systems in which there is more than one CPU.

On a mainframe or in a logical partition ( LPAR ) of a mainframe with more than one I-stream, TPF is said to be running tightly-coupled.

Due to the reentrant nature of TPF programs and the control program, this is made possible as no active piece of work modifies any program.

TPF is capable of supporting multiple mainframes ( of any size themselves-be it single I-stream to multiple I-stream ) connecting to and operating on a common database.

However when the lock is obtained offboard of the TPF processor in the DASD control unit, an external process must be used.

TPF application source code is typically kept in PDSs on a z / OS system.

Currently the z / OS compiler / assembler is used to build TPF code into object modules, producing load files that the TPF " online system " can accept.

Using TPF requires an intimate knowledge of the Operations Guide since there is no shipped support for any type of online command " directory " that you might find on other platforms.

TPF is highly optimized to permit messages from the supported network to either be switched out to another location, routed to an application ( specific set of programs ) or to permit extremely efficient accesses to database records.

With the advent of z / TPF, all programs will reside in core-eventually-the only question is when they get fetched the first time.

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 '.

In Montbovon there is a connection to the TPF ( previously GFM ) network.

TPF evolved from the Airlines Control Program ( ACP ), a free package developed in the mid-1960s by IBM in association with major North American and European airlines.

In 1979, IBM introduced TPF as a replacement for ACP — and as a priced software product.

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

Currently, 32 IBM mainframes may share the TPF database ; if such a system were in operation, it would be called 32-way loosely coupled.

Commands created by IBM and shipped by IBM for the running and administration of TPF are referred to as " Z-messages " as they are all prefixed with the letter " Z.

Since IBM hardware does I / O via the use of channels and channel programs, TPF would generate very small and efficient channel programs to do its I / O-all in the name of speed.

* TPF Information Center ( IBM )

* z / TPF ( IBM )

" 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.

See also IBM Airline Control System ( ALCS ), a variant of TPF specially designed to provide all the benefits of TPF ( very high speed, high volume, high availability transaction processing ) but with the advantages such as easier integration into the data center offered by running on a standard IBM operating system platform.

* Official IBM TPF website

Programmed Airline Reservations System ( PARS ) is an IBM proprietary large scale airline reservation application, a computer reservations system, executing under the control of IBM Airline Control Program ( ACP ) ( and later its successor, Transaction Processing Facility ( TPF )).

SabreTalk is a dialect of PL / I for the S / 360 IBM mainframes running the TPF platform.

In December 1979, ACP became known as ACP / TPF and then just TPF ( Transaction Processing Facility ) as the transaction operating system became more widely implemented by businesses other than the major airlines, such as online credit card processing, hotel and rental car reservations, police emergency response systems, and package delivery systems.

The high performance PARS operating system evolved from ACP ACP ( Airlines Control Program ) to TPF ( Transaction Processing Facility ).

His decNumber decimal package is also available as open source under several licenses and is now part of GCC, and his proposals for decimal hardware have been adopted by IBM and are integrated into the IBM Power6 and IBM System z10 processor cores, and in numerous IBM software products such as DB2, TPF ( in Sabre ), WebSphere MQ, operating systems, and C and PL / I compilers.

The z / VSE Version 4, z / TPF Version 1 and z / VM Version 5 operating systems, and presumably their successors, require z / Architecture.

Multiple operating systems are compatible with LPARs, including z / OS, z / VM, z / VSE, z / TPF, AIX, Linux, i / OS and Lotus Domino.

It is a variant of TPF specially designed to provide all the benefits of TPF ( very high speed, high volume, and high availability in transaction processing ) but with the advantages such as easier integration into the data center offered by running on a standard IBM operating system platform.

In the new z / TPF, the system itself will try to load balance by routing any application that does not request a preference or affinity to I-streams with less work than others.

A good example of the TPF system doing this can be found with TPFs support of I-stream unique globals.

So if you had defined a record type in the TPF system of ' FRED ' and gave it 100 records or ordinals, then in a processor shared scheme record type ' FRED ' ordinal ' 5 ' would resolve to exactly the same file address on DASD-clearly necessitating the use of a record locking mechanism.

All processor shared records on a TPF system will be accessed via exactly the same file address which will resolve to exactly the same location.

There are some other types of trace information that TPF can collect in core while running, and this information gets " dumped " whenever the system encounters a severe error.

Historically all data on the TPF system had to fit in fixed record ( and core block ) sizes of 381, 1055 and 4K bytes.

With the advent of C-support, application programs were no longer limited to 4K sizes, much larger C programs could be created, loaded to the TPF system as multiple 4K records and read into memory during a fetch operation and correctly reassembled.

z / TPF, which became available in December, 2005, also requires a 64-bit system.