DB2 and the Coupling Facility fail

If the Coupling Facility fails, the queue manager might fail, and DB2 will also fail if it is using this Coupling Facility.

Recover DB2 using DB2 recovery procedures. When DB2 has been restarted, we can restart the queue managers. The CF administration structure will also have failed, but this is rebuilt by restarting all the queue managers within the queue-sharing group.

If a single application structure within the Coupling Facility suffers a failure, the effect on the queue manager depends on the level of the queue manager and the CFLEVEL of the failed CF structure:

• If the CF application structure is CFLEVEL(3) or higher and RECOVER is set to YES, it will not be usable until you recover the CF structure by issuing an MQSC RECOVER CFSTRUCT command to the queue manager that will do the recovery. We can specify a single CF structure to be recovered, or we can recover several CF structures simultaneously. The queue manager performing the recovery locates the relevant backups on all the other queue managers' logs using the data in DB2 and the bootstrap data sets. The queue manager replays these backups in the correct time sequence across the queue sharing group, from just before the last backup through to the point of failure. If a recoverable application structure has failed, any further application activity is prevented until the structure has been recovered. If the administration structure has also failed, all the queue managers in the queue-sharing group must be started before the RECOVER CFSTRUCT command can be issued. All queue managers can continue working with local queues and queues in other CF structures during recovery of a failed CF structure.

• If the CF application structure is CFLEVEL(3) or higher and RECOVER is set to NO, the structure is automatically reallocated by the next MQOPEN request performed on a queue defined in the structure. All messages are lost, as the structure can only contain non-persistent messages.

• If the CF application structure has a CFLEVEL less than 3, the queue manager fails. On queue manager restart, peer recovery attempts to connect to the structure, detect that the structure has failed and allocate a new version of the structure. All messages on shared queues that were in CF structures affected by the Coupling Facility failure are lost.

If the structure has experienced a connection failure, the queue manager fails. On queue manager restart (after the connection failure has been rectified), the connection is reestablished, but no recovery takes place for a structure at any CFLEVEL.

See WebSphere MQ Script (MQSC) Command Reference for details of the RECOVER CFSTRUCT command.