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From Tomcat Novice <>
Subject Tomcat Thread utilization growing very large causing a hung tomcat instance
Date Tue, 03 Aug 2010 14:21:55 GMT

I hope someone can help me. I am new to tomcat and I have been encountering
issues where a particular tomcat instance/s are having large thread count
during load testing and results in a hung state. The error shown on the
browser is: java.lang.OutOfMemoryError: unable to create new native thread
(stack trace attached)


OS: Windows 2003 64 bit
JDK 1.5
8GB Total Machine RAM
4 Tomcat 5.5 instances running as a service on one Physical Server (each
Tomcat configured to use 1.5GB of Heap) 4 instances x 1.5GB = 6GB of Heap
4 Identical servers configured the same way and load balanced
IIS Web Server front end (AJP Port configured) no maxThreads property is set
on server.xml for AJP port declaration. Per documentation (, if no value is set
maxThreads are set to 200

Not all 4 servers are experiencing this problem.

1. Any ideas how I can resolve/isolate this problem?
2. I know I need to do a thread dump but I am not familiar on how to analyze
thread dumps from Tomcat. Can you point me to documententation on how I can
analyze thread dumps from Tomcat?
3. Also, can someone confirm if the thread dumps from JDK 1.5 are the same
as the Thread Dumps from a JDK 1.6? I seem to be getting different formats.
Can someone just confirm?
4. If the maxThread is set to 200, why are the Tomcat instances utilizing up
to 400 Threads (see screenshot)


Tomcat Novice

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