Two XRF complexes with three CPCs

You can have two XRF complexes running on three CPCs as shown in the following figure, providing adequate real and virtual storage is available on the CPC that runs the two alternate subsystems.

This configuration provides an advantage over two XRF complexes in four CPCs; your alternate IMS systems both run in a single CPC, eliminating the need for one VTAM®, one z/OS®, and one CPC. This configuration consists of:

• Three CPCs, z/OSs, and VTAMs
• Four IMS systems—two active IMS systems and two alternate IMS systems
• IMS system logs for each active subsystem and shared by its alternate IMS
• Databases shared by the active IMS and alternate IMS in each complex
• Remote terminals using SNA protocol and communicating with one or both of the active IMS systems
• If your XRF complex uses USERVAR, NCP running in each 37x5 Communication Controller that is attached to the CPCs

Figure 1. Two XRF complexes in three CPCs

Paths must exist to both the active and alternate subsystems for users of each subsystem. Each database must have shared access, either online or switchable at takeover, to its associated active and alternate CPC.