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From dcheckoway <>
Subject Help understanding memory usage/limits
Date Fri, 02 Apr 2010 11:30:34 GMT

I could use some help understanding memory usage & limits in activemq.  5.3.1
is what I'm running, fwiw.

1. Out of the box, <systemUsage> in activemq.xml is commented out.  I'm
passing ACTIVEMQ_OPTS="-Xmx2048M ...".  What is the default behavior in that
case?  Does that mean activemq will take advantage of the 2gb heap by
default, or do I need to configure <memoryUsage> explicitly?  If it needs to
be explicit, can I safely set <memoryUsage limit="2 gb"/> ?  If not, what's
a recommended setting given -Xmx2048M?

2. On <policyEntry>, what exactly does "memoryLimit" do?  I have
producerFlowControl="false", and I wasn't sure if memoryLimit only applies
when producer flow control is enabled, or what?

3. What happens if you set the <policyEntry> elements' memoryLimit to the
same size as your heap and/or <memoryUsage limit>?

I'd like to understand the interaction of all of these factors.  Any info
you can provide would be MUCH appreciated!!!

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