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From "Joseph Morgan" <>
Subject RE: Is IBM Right About Java?
Date Tue, 08 Feb 2011 16:36:19 GMT
I have a JVM heap monitor that sends emails when the upper limit
changes, and this appears to be true.  The GC still works, that is, used
heap continues to fluctuate up and down within the current upper limit,
but if the server experiences a hit on load and increases the heap, it
remains at that level.  

I have not yet seen it release heap, however, our servers have never
grown beyond about 15% of max memory available.  I wonder if when it
starts bouncing around 90%-95%, will it start to release heap.

-----Original Message-----
From: Robinson, Eric [] 
Sent: Tuesday, February 08, 2011 10:27 AM
To: Tomcat Users List
Subject: Is IBM Right About Java?

Saw this statement on an IBM web site:

"Most JVMs grow towards the upper heap limit (-Xmx/-mx options) when
more memory is required, and do not return memory to the operating
system, even if the memory is no longer needed, until the JVM process

Is this true? If thought returning unneeded memory to the OS was what GC
is all about.

Eric Robinson

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