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Getting JVM Heap Size

Posted on 2009-07-11
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Last Modified: 2013-12-11
I am trying to find ways to the current Heap size of a JVM

For example if the max jvm size is 100 MB, I want a shell script or a java program or C program to check the HEAP size used by the JVM at any given point of time. I have searched the whole internet I could not find anything useful. If anyone can help me that should be great.
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Question by:madhuthetom
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14 Comments
 
LVL 92

Expert Comment

by:objects
ID: 24830592
not sure there is a way from outside the jvm
see here for getting it within the jvm
http://www.exampledepot.com/egs/java.lang/GetHeapSize.html
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Expert Comment

by:objects
ID: 24830597
and it would depend on the vm's being used
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Expert Comment

by:CEHJ
ID: 24830988
You can get that info from outside the vm using jmap. See

http://it.toolbox.com/blogs/web2-place/how-to-get-details-on-jvms-heap-utilization-10609
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LVL 41

Expert Comment

by:HonorGod
ID: 24831034
You mean the current heap utilization, or the maxHeapSize value?

If you mean that you want to analyze the heap utilization, you're going to have to use the PMI, as discussed here:

http://publib.boulder.ibm.com/infocenter/wasinfo/v7r0/index.jsp?topic=/com.ibm.websphere.nd.doc/info/ae/ae/tprf_monitoringhealth.html

If you want to get the maxHeapSize, that is much easier, e.g., something like this:
# This only works for an unManaged Server.
#---------------------------------------------------------------------
server = AdminConfig.list( 'Server' );
node   = AdminControl.getNode();
mHS    = AdminTask.showJVMProperties('[-serverName %s -nodeName %S -propertyName maximumHeapSize]' % ( server, node ) )
 
print 'Max Heap Size for server %s on node %s is %s' % ( server, node, mHS );

Open in new window

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Author Comment

by:madhuthetom
ID: 24832073
HI thanks a lot for the idea.

But I Dont want to get the heap size for WAS server . I need to do it for websphere message broker
Borker does not expose any mbeans.so it has to be done only in shell script or C or java
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LVL 41

Expert Comment

by:HonorGod
ID: 24832185
Isn't message broker a WebSphere Application Server application?

What version of Message Broker are you using?

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Author Comment

by:madhuthetom
ID: 24832698
I am using WMB 6.1
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Expert Comment

by:guneshraj
ID: 24834010
Please read about Java's Profiling (& related protocols), this could be done easily.
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Expert Comment

by:dipinci
ID: 24834206
1. Are you looking to report the jvm (min /max) parameters being set for an exgrp?

This can be obtained by mqsireportproperties command
mqsireportproperties BrokerName -e ExgrpName -o ComIbmJVMManager -a

Or

2. Are you looking for JVM running within the biphttplistener process

I think there is no mqsiproperties to report the value, but the default value is 192MB.

To change the value,modify the message broker registry.

Windows

Under the registry key HKEY_LOCAL_MACHINE\SOFTWARE\IBM\WebSphereMQIntegrator\2\<BrokerName>\CurrentVersion create a new String value named MaxJVMHeapSize. Set this new String value to the JVM maximum heap size required in bytes. For example: 536870912 for 512 MB.

UNIX

In the directory <Broker File Path>/<Broker Name>/CurrentVersion/, create a new file named MaxJVMHeapSize. Set the contents of this file to the JVM maximum heap size required in bytes. For example: 536870912 for 512 MB.

For the changes to take affect, you will to stop and restart Message Broker.

or

3) If you are  looking for value of heap size occupied by exgrp jvm at a given point

 a)you can explore JVM  profiling as explained by Guneshraj.

 b) set the following in broker profile  
export MQSIJVERBOSE=-verbose:gc
This way, broker publishes an xml msg with details of exgrp jvm.
 it only publishes only when the exgrp starts up, not after that (ie: not periodically or so..)

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LVL 41

Expert Comment

by:HonorGod
ID: 25832671
Based upon the original question, http://#a24831034 appears to provide the most accurate answer to it.
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Expert Comment

by:dipinci
ID: 25833568
Based on author requirement the answer for the question is ID: 24834206.
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Accepted Solution

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madhuthetom earned 0 total points
ID: 25840033
I dont agree, Thats not what I watned. I have found the solution

I created a java compute node using java.lang.management to determine the help size, once it goes to 90% usage or more and sustains in high utilization for a while, I spin off another JVM instance.

But thanks to all for the help
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