In Figure 1, a log stream was defined in the LOGR policy with STG_DUPLEX(YES) DUPLEXMODE(COND). Two systems are connected to the log stream. The coupling facility structure associated with the log stream is in a stand-alone CPC. The coupling facility for the structure is volatile, therefore both systems will duplex the data to staging data sets because there might be a single point of failure for both systems.

Figure 1. Example: Using Staging Data Sets When the Coupling Facility is Volatile

If the coupling facility was non-volatile, neither system would duplex their coupling facility data to staging data sets, but would maintain local buffers on each system.

If the installation had specified STG_DUPLEX(YES) DUPLEXMODE(UNCOND), both systems would duplex data to staging data sets, regardless of the volatility of the coupling facility.

If the installation had specified STG_DUPLEX(NO), neither system would duplex to staging data sets (under normal circumstances).