Question & Answer
Question
You had persistent and persistent messages stored in queues in a multi-instance queue manager.
After a failover/switchover, the Standby instance became the new Active instance.
But you noticed that some messages were discarded and are no longer in the queues!
What happened?
After a failover/switchover, the Standby instance became the new Active instance.
But you noticed that some messages were discarded and are no longer in the queues!
What happened?
Answer
a) The messages that are no longer in the queues after a failover/switchover are non-persistent messages.
By definition, non-persistent messages might be lost during a restart of a queue manager, because they "live" in memory of the host of the Active instance and not in disk.
The contents of the memory is not shared among the hosts: the memory used by the Active is not copied into the memory of the Standby.
The persistent messages, on the other hand, live in disk and in memory, and because of the storage in disk, these messages are available after a restart.
It might be a subtle distinction, but you need to keep in mind that when a Standby becomes the new Active instance, it is doing a full restart of the queue manager!
The failover of the Activate instance of a multi-instance queue manager triggers the Standby instance to start the queue manager.
Notice the keyword "start", which means that non-persistent messages might be lost during the failover.
b) For more information on recovery after a failover/switchover/reconnection see:
https://www.ibm.com/support/knowledgecenter/en/SSFKSJ_9.1.0/com.ibm.mq.con.doc/q018380_.htm
IBM MQ 9.1.x / IBM MQ / Configuring / Configuring high availability, recovery and restart / High availability configurations / Multi-instance queue managers /
Application recovery
.
It might be a subtle distinction, but you need to keep in mind that when a Standby becomes the new Active instance, it is doing a full restart of the queue manager!
The failover of the Activate instance of a multi-instance queue manager triggers the Standby instance to start the queue manager.
Notice the keyword "start", which means that non-persistent messages might be lost during the failover.
b) For more information on recovery after a failover/switchover/reconnection see:
https://www.ibm.com/support/knowledgecenter/en/SSFKSJ_9.1.0/com.ibm.mq.con.doc/q018380_.htm
IBM MQ 9.1.x / IBM MQ / Configuring / Configuring high availability, recovery and restart / High availability configurations / Multi-instance queue managers /
Application recovery
.
+++ end +++
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Document Information
Modified date:
23 April 2020
UID
ibm16198855