Overview of System-Managed Rebuild Processing

System-managed processing provides a means for rebuilding or duplexing a structure with minimal participation from connectors to the structure. During a system-managed process, connectors receive events that delineate the period during which the structure is unavailable for requests. During that time, the system defers accesses to the structure, manages the old and new structure instances that exist during the process and propagates data to the new structure. At the conclusion of the system-managed process, connectors receive one or more events notifying them of any changes to the structure.

The two types of system-managed processing are rebuild and duplexing rebuild.

Rebuild is intended for planned reconfiguration scenarios. The system allocates the new structure, propagates the necessary structure data to the new structure, and then switches over to using the new structure instance.
Duplexing rebuild is intended to provide a failure recovery capability through failover to the unaffected structure instance. The system performs the significant steps in the duplexing rebuild process, including allocating the secondary (new) instance of the structure, attaching users to the new structure instance, copying all necessary data from the primary (old) instance to the secondary instance, and then transparently duplexing coupling facility operations to both instances of the structure.

System-managed processing can function as long as the old and new structures remain viable and there is at least one system in the sysplex capable of performing the required system-managed processing. Connectors can specify that they support system-managed processing even if they do not support user-managed rebuild or duplexing rebuild.

During a system-managed process, the system defers any requests that are submitted while the structure is unavailable. The requests will be processed after the rebuild process has completed, been terminated, or for duplexing rebuild, reached the duplexed established phase. In a system-managed process, connectors are not required to cease their operations against the structure before responding to the event signifying that the structure is unavailable. However, IBM® recommends that they do so to minimize the system resources required to quiesce activity against the structure.

System-managed rebuild is supported only for planned reconfiguration. When the coupling facility or the structure has failed, or when any active connectors have lost connectivity, system-managed rebuild will not be used to rebuild the structure.

System-managed rebuild has the following requirements:

The structure must be allocated in a coupling facility of CFLEVEL=8 or higher.
The CFRM couple data set must have been formatted with the ITEM NAME(SMREBLD) NUMBER(1) statement and be active as the primary CFRM couple data set. In order to activate the CFRM couple data set, all systems using the CFRM couple data set must be at OS/390® Release 8 or higher.
A list structure or lock structure with record data must have been allocated by a system at OS/390 Release 8 or higher in order for system-managed rebuild to occur.

System-managed duplexing rebuild is intended to provide a robust failover capability through the creation and maintenance of a duplex copy of a structure in advance of any failure. However, when the coupling facility or the structure has failed, or when any active connectors have lost connectivity, system-managed duplexing rebuild will not be used to rebuild the structure.

System-managed duplexing rebuild has the following requirements:

The structure must be allocated in a coupling facility of CFLEVEL=11 or higher.
CF-to-CF links must be available.
The CFRM couple data set must have been formatted with the ITEM NAME(SMDUPLEX) NUMBER(1) statement and be active as the primary CFRM couple data set. In order to activate the CFRM couple data set, all systems using the CFRM couple data set must be at z/OS® Release 2 with OW41617 installed.
A list structure or lock structure with record data must have been allocated by a system at OS/390 Release 8 or higher in order for system-managed duplexing rebuild to occur.