Introduction to the z/TPF system

The z/TPF system provides an extremely responsive solution to very high volume online processing that is required in many business enterprises. The z/TPF system has wide acceptance within the airline industry but is also used in non-airline applications for processing relatively simple inquiry and response messages associated with a large population of terminals and workstations. The z/TPF system is most commonly used for the purpose of accessing a large centralized database that is an inventory of business information.

The z/TPF system is a high availability operating system designed to provide quick response times to high volumes of messages from large networks of terminals and workstations. A typical z/TPF system handles several hundred messages per second. A typical network varies from several hundred terminals and workstations to tens of thousands. The response time of the z/TPF system within a network is typically less than three seconds from the time the user sends a message to the time the user receives a response to that message. High availability is enhanced by the ability to quickly restart the system; restarting after a system failure takes between 30 seconds and two minutes.

These factors result in the unique design of the z/TPF system that can be summarized as:

Efficient use of resources, such as main storage and file storage
Short path lengths for critical system services, such as direct access storage device (DASD) input/output (I/O)
Open-ended capacity growth, such as coupling as many as 32 multiprocessor z/Architecture® configurations with only a minimal increase in system overhead and expandable database capacity by adding DASD
High throughput while maintaining quick response times
High availability allows for 24-hour, 7-day a week operation
Database integrity and online database maintenance capability.

A z/Architecture ^¹ configuration (see Figure 1), used by the z/TPF system, incorporates multiple central processing units (CPUs) that are packaged together to share main storage. Therefore, a z/Architecture configuration is defined as a channel subsystem and a set of CPUs that share main storage.

The z/TPF system also supports interconnected z/Architecture configurations by using the z/Architecture channel subsystem. In particular, multiple z/Architecture configurations can be interconnected through z/Architecture channel-to-channel (CTC) communication. In a fiber optic channel environment, an Enterprise Systems Connection (ESCON) channel, which operates in CTC mode, supports the CTC communication.

The term central processor complex (CPC) is used within the z/TPF information to denote an z/Architecture configuration that is attached by using locally attached channel subsystems to a set of devices or other z/Architecture configurations. z/Architecture configuration and central processor complex (CPC) are described in z/TPF system processing. The computing facilities that are housed at a single location, which can include interconnected z/Architecture configurations, is viewed as a processing center, as shown in Figure 1.

Alternate text — Figure 1. A processing center

Terminals and workstations are attached to a central processor complex (CPC) through wide area communication facilities. The phrase wide area communication facility means the use of transmission services provided by common communication carriers, which take two forms:

Communications channels that are leased for the exclusive use of the z/TPF system, usually called private lines. Terminal concentrators are attached to these lines, forming a private network.
Local access lines that are leased to attach to a common communication carrier data network that can be shared with other enterprises. Terminal concentrators are also attached to remote access points. (Remote is relative to a CPC; the terminal concentrators also attach through a local access line.) The management of the long distance routing and transmission, in this case, is the responsibility of the common carrier.

Processing centers can be linked together into networks through wide area communication facilities.

¹ In this information, the term z/Architecture means the hardware architecture that is described in z/Architecture Principles of Operation, also referred to as Principles of Operation.