OpenTP1 enables transaction processing even in distributed systems where some of the required data or applications are contained in a non-OpenTP1 system, such as a large-scale computer. For example, an organization might have a mainframe connected via a WAN to LANs at work sites and branch offices (Figure 1-8). In this configuration, a workstation or PC can use messages to exchange data with the host computer. A message can send data to the large-scale computer for processing, and the results can be returned by another message. This process can be managed as a transaction controlled by OpenTP1.

Figure 1-8 shows an example of how a distributed system can be configured.

Figure 1-8 OpenTP1 online transaction processing in a system using a large-scale host computer