z/TPF system structural characteristics summary

The following is, in effect, a detailed introduction to the z/TPF system resource management facilities, done in the context of tracing the flow of a message through the system. Data organization and storage and Data communications, provide additional important structural details.

An operational system is a combination of the z/TPF system, application programs, and people. People assign purpose to the system and use the system. The creation of an operational system depends upon three interrelated concepts:

System definition, which is the necessary application and z/TPF system knowledge required to select the hardware configuration and related values used by the z/TPF system software.
System initialization, which is the process of creating the z/TPF system tables and configuration-dependent system software.
System restart and switchover, which are the procedures used by the z/TPF system software to ready the configuration for online use.

System generation and system initialization are collectively called system generation. System definition is a design phase when installing a z/TPF system.

System restart is the component that uses the results of a system generation to place the system in a condition to process real-time input. The initial startup is a special case of restart and, for this reason, system restart is usually called initial program load or IPL. System restart uses values found in tables set up during system generation and altered during the online execution of the system. A switchover implies shifting the processing load to a different z/Architecture® configuration. A restart or switchover may be necessary for either a detected hardware failure, a detected software failure, or operator option.