A coupling facility becomes non-volatile

If a coupling facility changes to a non-volatile state, the system logger on each system using the coupling facility structure is notified.

For simplex-mode structures, system logger may change the way it duplexes coupling facility data because the change to a non-volatile coupling facility may have removed the single point of failure condition.

Assume the initial environment had a volatile structure coupling facility state and there was a failure-dependent relationship between the connecting system and the structure.
The log stream was considered to be in a single point of failure environment and continues to be after the state change, so system logger makes no changes to the duplexing method.
Assume the initial environment had a volatile structure coupling facility state and there was a failure-independent relationship between the connecting system and the structure.
System logger may then change the way it duplexes coupling facility data because the non-volatile coupling facility no longer constitutes a single point of failure.
- System logger will duplex the log data using local buffers, unless the log stream definition specified STG_DUPLEX(YES) DUPLEXMODE(UNCOND).

For duplex-mode structures, system logger may also change the way it duplexes coupling facility data because the change to a non-volatile coupling facility may have removed the single point of failure condition.

Assume the initial environment had a volatile composite structure coupling facility state but there was a failure-dependent relationship between the connecting system and the composite structure view.
The log stream was considered to be in a single point of failure environment and continues to be after the state change (because of the failure-dependent connection), so system logger makes no changes to the duplexing method.
Assume the initial environment had a volatile composite structure coupling facility state and there was a failure-independent connection between the connecting system and the composite structure view, but there was a failure-dependent relationship between the two structure instances.
The log stream was considered to be in a single point of failure environment, but would not be after the coupling facility state changes to non-volatile. System logger would continue to duplex the log data, but might change the duplexing method.
- The data will be duplexed by system logger using local buffers, unless staging data sets were specifically requested by having STG_DUPLEX(YES) DUPLEXMODE(UNCOND) on the log stream definition.
Assume the initial environment had a volatile composite structure coupling facility state, there was a failure-independent connection between the connecting system and the composite structure view, and there was a failure-independent relationship between the two structure instances.
The log stream was considered to be in a single point of failure environment, but would not be after the coupling facility state changed to non-volatile.
- For log streams defined with LOGGERDUPLEX(UNCOND), system logger will continue to duplex the log data.
  - The data will be duplexed by system logger using local buffers, unless staging data sets were specifically requested by having STG_DUPLEX(YES) DUPLEXMODE(UNCOND) on the log stream definition.
- For log streams defined with LOGGERDUPLEX(COND), system logger will stop providing its own duplexing because the system-managed duplexed structure provides sufficient back-up capability for the log data.