Transaction Processing Facility

TPF is an IBM real-time operating system for mainframes descended from the IBM System/360 family, including zSeries and System z9. The name is an initialism for Transaction Processing Facility.

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. The new name suggests its greater scope and evolution into non-airline related entities.

Current users include Sabre (reservations), Amadeus (reservations), VISA Inc (authorizations), American Express (authorizations), EDS SHARES (reservations), Holiday Inn (central reservations), CBOE (order routing), Singapore Airlines, Emirates, KLM, Garuda Indonesia, Amtrak, Marriott International, Travelport and the NYPD (911 system).

TPF delivers fast, high-volume, high-throughput transaction processing, handling large, continuous loads of essentially simple transactions across large, geographically dispersed networks. The world's largest TPF-based systems are easily capable of processing tens of thousands of transactions per second. 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. This is due in part to the multi-mainframe operating capability and environment.

While there are other industrial-strength transaction processing systems, notably IBM's own CICS and IMS, TPF's raison d'être is extreme volume, large numbers of concurrent users and very fast response times, for example VISA credit card transaction processing during the peak holiday shopping season.

TPF implements an application known as PARS. Many airlines use this passenger reservation application or its international version IPARS. TPF was traditionally a 370 assembly language environment for performance reasons, and many TPF assembler applications persist. However, more recent versions of TPF encourage the use of C. Another programming language called SabreTalk was born and died on TPF. One of TPF's major components is a high performance, specialized database facility called TPFDF.

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. All these operating systems usually coexist on the same physical hardware since IBM mainframes feature multiple ways of partitioning, to handle mixed workloads.

IBM announced the delivery of the next release of TPF, dubbed z/TPF V1.1, in September 2005. Most significantly, z/TPF adds 64-bit addressing and mandates use of the 64-bit GNU development tools. The GCC compiler and the DIGNUS Systems/C++ and Systems/C are the only supported compilers for z/TPF. The Dignus compilers offer reduced source code changes when moving from TPF 4.1 to z/TPF. Japan Airlines has publicly acknowledged they are running z/TPF.