This topic applies to coupling facility log streams only. If a coupling facility structure changes modes, the system logger on each system using the coupling facility structure is notified.

System logger's behavior after a structure switches from simplex-mode to duplex-mode or vice versa depends on whether a single point of failure environment exists after the mode switch and the duplexing specifications for the structure and the log streams within the structure.

It is possible for system logger to change from using local buffers to staging data sets or to change from using staging data sets to local buffers. It is also possible for logger to start providing its own duplexing of the log data or stop duplexing the log data after the mode switch.

See Selecting a method of duplexing coupling facility log data for additional details about log data duplexing specifications and considerations. In particular, see Table 1.