Connecting to a Structure During User-Managed Duplexing Rebuild

User-managed duplexing rebuild allows connectors to request that a second instance of the structure be allocated in another coupling facility for the purpose of duplexing the data in each structure to achieve increased availability and usability. The duplexing process also allows you to change the attributes of the original structure. Connectors to the structure being duplexed can copy data from the old structure to the new structure. Once the structure is duplexed (Duplex Established phase), connectors synchronize their use of both structures. At any time it is possible to discontinue the duplex process and either fall back to using the original structure or switch (forward complete) to use the secondary structure. See Overview of User-Managed Rebuild Processing for a description of the structure duplexing process.

Depending on the phase of the duplexing process, you might or might not be allowed to connect to the structure that is being duplexed. IXLCONN sets the following return codes when you request a connection to a structure that is being duplexed:

IXLCONN sets a return and reason code (IXLRSNCODESPECIALCONN) to indicate that additional status information is available. The same two bits in the CONAFLAGS field (CONAREBUILD and CONAREBUILDSTOP) in IXLYCONA that are used by structure rebuild also report the status of a duplexed structure. Additionally, a bit in the CONAREBUILDFLAGS field indicates whether the rebuild in progress is a duplexing rebuild. See Handling New Connections During a User-Managed Rebuild Process for additional information about the IXLRSNCODESPECIALCONN reason code.
IXLCONN also might set a return and reason code (IXLRSNCODECONNPREVENTED) to indicate that a new connection is not permitted at this time because all active connectors have confirmed the Duplex Rebuild Complete event and must complete their cleanup of one instance of the structure. New connections are not permitted until all active connections have provided an event exit response to the Rebuild Cleanup event. New connections also are not permitted if a request to stop the duplexing rebuild to fall back to using the old structure is received.

Connections to duplexed structures are allowed throughout most phases of the duplexing operation, and the connectors are expected to participate in the duplexing process. The connect answer area identifies the phase of duplexing the structure is in and whether switch processing is in progress. See Handling New Connections During a User-Managed Rebuild Process.

Connections to structures in the Duplex Established phase while structure alter is being processed for the duplexed structure are also allowed. See Altering a Duplexed Structure for a description of structure alter for a duplexed structure.