Minimise coupling facility (CF) accesses during CF recovery from backup and logs
Original Publication Date: 2002-Jun-16
Included in the Prior Art Database: 2003-Jun-18
OVERVIEW Disclosed is a technique to minimise the number of coupling facility accesses needed to restore shared queue messages of a message broker such as IBM's MQSeries* for OS/390* product held in a coupling facility list structure from a prior fuzzy backup of that list structure and changes to that list structure held in recovery logs. The technique exploits the fact that the coupling facility recovery process has exclusive access to the list structure during list structure recovery. This means that the rules which apply to list structure updates during normal operation need not apply during the recovery process. All that matters is that the list structure is correct at the end of the recovery process. It does not need to be correct at all times during the recovery process. BACKGROUND Some message brokers (eg the MQSeries product for OS/390) have support for shared queues. Shared queue messages are stored as list entries in one or more coupling facility (CF) list structures. Applications running on multiple queue managers in the same queue sharing group (QSG) anywhere in a parallel sysplex can then access these shared queue messages. This provides continuous availability, scalable capacity, and automatic pull workload balancing.