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Recovery and restart
A messaging system ensures that messages entered into the system are delivered to their destination. This means that it must provide a method of tracking the messages in the system, and of recovering messages if the system fails for any reason.
WebSphere MQ ensures that messages are not lost by maintaining recovery logs of the activities of the queue managers that handle the receipt, transmission, and delivery of messages. It uses these logs for three types of recovery:
- Restart recovery, when you stop WebSphere MQ in a planned way.
- Crash recovery, when a failure stops WebSphere MQ.
- Media recovery, to restore damaged objects.
In all cases, the recovery restores the queue manager to the state it was in when the queue manager stopped, except that any in-flight transactions are rolled back, removing from the queues any updates that were in-flight at the time the queue manager stopped. Recovery restores all persistent messages; nonpersistent messages can be lost during the process.
The rest of this chapter introduces the concepts of recovery and restart in more detail, and tells you how to recover if problems occur. It covers the following topics:
- Making sure that messages are not lost (logging)
- Using checkpointing to ensure complete recovery
- Calculating the size of the log
- Managing logs
- Using the log for recovery
- Protecting WebSphere MQ log files
- Backing up and restoring WebSphere MQ
- Recovery scenarios
- Dumping the contents of the log using the dmpmqlog command
- Making sure that messages are not lost (logging)
- Using checkpointing to ensure complete recovery
- Calculating the size of the log
- Managing logs
- Using the log for recovery
- Protecting WebSphere MQ log files
- Backing up and restoring WebSphere MQ
- Recovery scenarios
- Dumping the contents of the log using the dmpmqlog command
Parent topic:
Recovery and problem determination
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