Multiple database function (MDBF)

The multiple database function (MDBF) of the High Performance Option (HPO) feature permits the physical and logical separation of sets of data within the z/TPF online modules. An example is an airline's reservation application that supports several airlines, each with their own unique reservation records but which share hardware and system resources.

When sets of data are separated physically, a set of data is accessible by a subsystem. When sets of data are separated logically, a set of data is accessible by a subsystem user. When sets of data are separated physically and logically, a set of data is accessible by a subsystem user within a subsystem. Refer again to Figure 1.

A subsystem can support multiple subsystem users. However, it is not necessary to define subsystem users.

The basic subsystem (BSS) is fundamental; at a minimum, the basic subsystem contains the sets of data required by the z/TPF system for its own operation and, therefore, must always exist. (A z/TPF system without MDBF is actually operating as a basic subsystem.)

Generating a z/TPF system with the multiple database function (MDBF) impacts the z/TPF system services and structures dealing with file management and message routing.