Damage to or failure of the coupling facility structure

If a coupling facility fails or is damaged, all systems connected to the coupling facility structure detect the failure. The first system whose system logger component detects the failure initiates the structure rebuild process. The structure rebuild process results in the recovery of one or more of the affected coupling facility structure's log streams. All the systems in the sysplex that are connected to the list structure participate in the process of rebuilding the log streams in a new coupling facility list structure.

When the rebuild starts, system logger issues an event 48 signal to inform applications that the rebuild is starting and that the log streams associated to the coupling facility structure that is being rebuilt are not available. Bits IXGENFStrRebuildStart and IXGENFLogStreamsNotAvailable are on in the event 48 parameter list mapped by macro IXGENF.

While the rebuild is in progress, system logger rejects any system logger service requests against the log stream. Applications must listen for another ENF event 48 to learn the status of the log stream after rebuild processing is complete. The status will be one of the following:

The structure rebuild has completed successfully, the coupling facility structure and associated log streams are available, and system logger requests will be accepted. Bits IXGENFLogStreamsAvailable and IXGENFStrRebuildComplete are on in the event 48 parameter list mapped by macro IXGENF.
The structure rebuild was unsuccessful and connection to the structure is not possible because the structure is in a failed state. Log data still resides in staging data sets if they are used to duplex the log data for the log stream. If staging data sets were not used, the data persists in the local storage buffers on each system. All system logger service requests against the log streams will be rejected. Bits IXGENFLogStreamsNotAvailable, IXGENFStrRebuildFailed, and IXGENFRebuildFailStrFail are on in the event 48 parameter list mapped by macro IXGENF.
In this case, applications connected to the affected log streams must wait for the structure to be rebuilt successfully and the system to issue an ENF 48 event to indicate that the log streams are available.