gtpa2m0a | Application Programming |
The original TPF system was designed to satisfy the requirements of airline reservations agents who access available flight space and record travelers' choices. TPF updates inventories, creates passenger name records, and maintains the indexes or other database support necessary to retrieve records for display or modification, if required. The agent communicates with a traveler by telephone, but accesses the necessary data using a terminal that is linked to a central computer through a communication network.
The airline reservations application still typifies the environment for which TPF provides the optimum solution. However, any data processing environment that requires remote users to access a large common database is a potential TPF user. TPF is implemented by a variety of business types, including banks, car rental companies, electronic funds transfer systems, hotel reservation systems, message switching networks, municipal government, and consumer finance companies.
Although applicable to a wide variety of application areas, TPF achieves its efficiency, in part, by limiting function and flexibility in favor of extremely high availability and rapid, consistent responses. The communications area supports a limited number of line protocols, as the following list indicates.
In the area of file storage support, use of both a single access technique and rigid formatting reduce operating system requirements. Other areas with concepts that contribute to the efficiency of TPF include the management of messages, working storage, and programs. The inherent complexity of a real-time system also requires development of special-purpose test procedures, test tools, and support functions.
TPF and its support reside in different environments. The primary real-time environment, under control of TPF serving the application function, is often referred to as the online system. Most of the secondary programs and facilities, which support the online system, operate in a batch-oriented environment under control of an MVS system. This environment is referred to as the offline system.
TPF uses backup equipment to satisfy its high availability requirements: the backup always is ready to carry the online function in the event of failure. The offline system may also use the backup equipment in a dual role to provide the tools for application development, maintenance of programs, maintenance of data, and batch processing of applications that are not real-time (for example, financial reports and data reduction of system measurements).