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From James Black <>
Subject systemUsage and destinationPolicy config
Date Mon, 03 Oct 2011 10:28:06 GMT

looking for some help around systemUsage and destinationPolicy configuration
as I'm having some difficulty fully understanding the relationship between
systemUsage, destinationPolicy, and flow control.

All our messages are persistent!  producerFlowControl is on.

So we give ActiveMQ say a maximum of 512MB heap space.

Our systemUsage is set as below:

            <memoryUsage limit="200 mb"/>
            <storeUsage limit="10 gb"/>
            <tempUsage limit="1000 mb"/>

Our destination policy as below:

        <policyEntry topic=">" producerFlowControl="true" memoryLimit="1mb">
        <policyEntry queue=">" producerFlowControl="true" memoryLimit="1mb">

Please verify the if the following is correct:

This means that for each individual queue/topic the memory limit is 1MB. 
What exactly happens when this 1MB is hit, does the queue block or does it
page to disc?

The total allowed memory for all queues and topics is 200MB.  Meaning that
we could have 200 channels operating at their full capacity of 1MB.  We
currently have 16 queues and topics in total so obviously that is never

Are we better to remove the individual policy entry on the memory limit and
share the memory between the various channels?

If we do this at what point would they block?

Any help very much appreciated!  Can paypal you some beer money!

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