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WebSphere Product WebSphere Applicat.. What is the maxium heap size we can allocate to...
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What is the maxium heap size we can allocate to single JVM?
3 years ago  ::  Dec 20, 2011 - 10:00PM #1
srikanth
UNIX SYSTEM ADMIN
CITI GROUP
Posts: 10
What is the maxium heap size we can allocate to single JVM?
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3 years ago  ::  Dec 21, 2011 - 1:13AM #2
Joseph
WebSphere Platform Technology Consultant
Consulting Ltd
Posts: 346
in one line......

it depends on your hardware configuration 
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3 years ago  ::  Dec 22, 2011 - 3:26PM #3
Jim
Manager Middleware
First Marblehead
Posts: 1
If you're running 32-bit WAS on UNIX, it's 2GB. If running 64-bit WAS it's effectively unlimited, limited to the amount of physical memory installed. If on UNIX, you'll need to subtract several GBs for operatnig system, etc.
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3 years ago  ::  Dec 22, 2011 - 8:59PM #4
Anandpal
Posts: 1
I f you are ruunig on WAS 32 bit then the theoritically maximum heap size you can use would be 4 GB ( 2 power 32) and if you are running on WAS 64 bit then its in teraa bytes (2 power 64).

 
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3 years ago  ::  Dec 23, 2011 - 2:59AM #5
Christoph
IT-Systemprogrammierer
KKH-Allianz
Posts: 41
However you should be aware of the performance impact of garbage collection when allocating large amounts of RAM to your java process.
The more RAM you allocate, the longer the garbage collection pauses get (stop the world). On our HP-UX IA64 Systems, we tend not to use more than 2GB HEAP (which results in about 4GB total RSS process memory) for our web application servers, as FULL GC pauses get as high as 6-8 seconds (which is already bad from a user perspective, as the applications become unresponsive for this time).
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3 years ago  ::  Dec 23, 2011 - 12:58PM #6
Joseph
WebSphere Platform Technology Consultant
Consulting Ltd
Posts: 346
I sugest you to follow this document to determine the heap usage in your application serving environment. Once the mertrics and trends are collected and analyzed.. it will be easy to decide what would be the good heap settings. 

www.websphereusergroup.org/josephamrithr... 
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3 years ago  ::  Dec 31, 2011 - 8:02AM #7
Alexei
BPM Consultant
IBM Brazil
Posts: 26
This might help too:

publib.boulder.ibm.com/infocenter/javasd...
 
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3 years ago  ::  Jan 02, 2012 - 3:34AM #8
Christoph
IT-Systemprogrammierer
KKH-Allianz
Posts: 41
Perhaps this will help, too:
www-304.ibm.com/support/docview.wss?uid=...
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3 years ago  ::  Jan 16, 2012 - 4:26AM #9
srikanth
UNIX SYSTEM ADMIN
CITI GROUP
Posts: 10
Thanks to All for the reply.
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