CODEWITHSUNDEEP
ibm-mq
arrehman
arrehman

Reputation: 1322

Clear messages from mq using java

What is the best approach to connect to websphere mq v7.1 and clear all the messages of one or more specified queues using Java and JMS? Do I need to use Websphere MQ specific java API? Thanks.

Upvotes: 2

Views: 4002

Answers (1)

T.Rob
T.Rob

Reputation: 31852

Like all good questions, "it depends."

The queue can be cleared with a command only if there are no open handles on the queue. In that case sending a PCF command to clear the queue is quite effective, but if there are open handles you get back an error. PCF commands are of course a Java feature and not JMS because they are proprietary to WebSphere MQ.

On the other hand, any program authorized to perform destructive gets off a queue can clear the queue. In this case, just loop over a get until you get the 2033 return code indicating the queue is empty. This can be performed using JMS or Java but both of these manage the input buffer for you. If the queue is REALLY deep then you end up moving all that data and if the app is client connected, you are moving it at network speed instead of in memory.

To get around this, you need to specify a minimal amount of buffer and as one of the GET options also specify MQGMO.TRUNCATED_MSG_ACCEPTED. This moves only the message header during the get calls and can be significantly faster.

Finally, if you are doing this programamtically and regardless of which method you use, spin off several threads and don't use syncpoint. You actually have to go out of your way to get exclusive input on a queue so once you get a session, just spawn many threads off of it. Close each thread gracefully and shut down the the session once all the threads are closed.

Upvotes: 2

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