gtpc3m0bConcepts and Structures

TPF System Overview

This section introduces the various elements that must be considered when describing the TPF system.

Although the emphasis of this publication is on the TPF production system, an appreciation and understanding of the other elements in the TPF environment is a necessary prerequisite for installing and operating the production system.

Note:
Historically, the TPF production system is called the online system and the supporting environment is called offline. These terms are pervasive throughout this publication and other TPF documentation.

TPF Production System

The production system is represented by system programs that manage the ESA hardware resources and interface with communication networks, as shown in Figure 2. The TPF main supervisor and related system programs are designed on the premise that work arriving at a central processing complex (CPC) arrives over data communication facilities in the form of a message. The term Entry is often used to describe an input message. Strictly speaking, an input message does not become an Entry until it is taken from an input queue and attached to an entry control block (ECB). Normally, an Entry processes one element of input data only. Thus, in contrast to batch processing systems that create tasks that can run for several hours, an Entry typically exists only for a few hundred milliseconds.

Note:
Unfortunately, the term entry is often used generically in the TPF documentation to denote an item within a group of related fields in a table or list. Using the word entry in this context is easily confused with the TPF process construct called an Entry, described above. In this publication, this documentation dilemma is suppressed by using phrases such as two-field item or work item; further, the word Entry is capitalized when it is used to refer to the TPF application process.

There is no such thing as a job in the TPF system, and there is no need to create a teleprocessing (TP) subsystem or monitor to run within the framework of a batch operating system as, for example, the Customer Information Control System (CICS), which runs under MVS. The penalty for the TPF design: batch processing and computationally intensive work are not easily accommodated by the TPF main supervisor, and applications of this sort are seldom run under TPF control. The reward of the design: a boost in performance because interactive work does not incur the system overhead associated with a TP monitor in a general purpose operating system.

The TPF production system maximizes the number of messages that can be processed in a unit interval of time, usually expressed as messages per second, while maintaining rapid response times to the end users who enter the messages. Response time is measured as the time between user initiation of an input message and the display of the first character of the reply message. A TPF transaction implies several system responses in answer to a sequence of related user input messages. The TPF production system manages a large database in real time, which means the system continues to run even during periods of database maintenance.

The TPF system is characterized by:

Supporting Environment

The supporting environment is used to develop and test the applications that are run on the production system, as well as to generate and maintain the production system itself.

Applications that run in the TPF production environment are developed using high-level assembler, C, or C++ programming language. These applications are assembled or compiled in the supporting environment using the MVS operating system.

The requirements of test facilities depend on the extent to which an enterprise develops applications. For an enterprise that purchases TPF applications, the requirements for test facilities can be minimal. However, for an enterprise that develops applications, a test facility that closely resembles the configuration of the production system is often desirable.

A test system that provides a reasonable simulation of the production environment can be run:

There are several aspects to the maintenance of the production system that must be considered:

System Backup and Recovery

System backup and recovery is the way in which an enterprise can recover its operation in the event of the unexpected. In today's business environment, the business of the enterprise is often heavily dependent on the availability of its TPF system, and so, it is necessary for an enterprise to understand, plan, and be prepared to prevent a single point of failure.

The planning and implementation of the hardware required for testing in a non-production environment is usually factored into an enterprise's business recovery plan.

A primary factor in planning and implementing business recovery is physical planning, and this ranges from what to do when there is a localized equipment failure (such as failure in a DASD controller or an ESA configuration) to a disaster (such as fire, earthquake, tornado, or act of terrorism).

In reality, enterprises that rely on a TPF system have plans that range from contracting with another enterprise to provide the physical resources to the other extreme where the enterprise has built into its physical environment precautions, such as locating the equipment underground and installing additional equipment. A compromise between these two extremes can be the sharing of equipment between a test configuration and the production system.