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I am using weblogic 10.3.6 with JRockit installed . I am using a 64 bit system with Linux as OS. I have an adf application installed in it . There are only a couple of users using the application . But the server machine where WLS is installed keeps going down every week causing out of memory . so we have to restart it every week. When i was looking through I found that WebLogic can be made more stable by adjusting the heap size and other memory arguments .

Example: --Xms256m --Xmx512m MaxPermsize as 128m

My question is

  1. What are these arguments ?

  2. How are these arguments related to one another?

  3. How do I determine the value for these arguments?

  4. What can be other causes for out of memory issue?

Thanks,

Rakesh

Sam
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2 Answers2

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Xms and Xmx are the minimum and the maximum heap (essentially where the objects are stored) size the java program can use.

In your case the java program is the WebLogic server on which your application is deployed. By default the Xms and Xmx values set by WebLogic server are : 256m and 512m.

Looks like your application needs more than 512MB heap memory. So you need to increase the maximum heap size (Xmx) to avoid frequent OutOfMemory error.

The new value of Xmx can be 1024m or more. You (or Performance team, if there is one.) have to do rigorous Performance, Scalability, Reliability testing with your application and with different Xmx values to determine what is the best for the application.

Setting the Memory Arguments (i.e Xms, Xmx) can be done at the script level (if you are using startWebLogic.sh/startManagedWebLogic.sh scripts to start the servers).

Script Level Changes:

  • Open setDomainEnv.sh and search for 'IF USER_MEM_ARGS the environment variable is set' and in the next line insert USER_MEM_ARGS="-Xms256m -Xmx1024m"
  • You can even change this setting from server to server by using SERVER_NAME variable which holds the server that is being started. For example to have this setting only for non-Admin servers, insert [ "${SERVER_NAME}" != "AdminServer" ] && USER_MEM_ARGS="-Xms256m -Xmx1024m"

Console Changes (Only if you use Admin Console to start the managed servers):

  • Login to AdminConsole–>Environments—>Servers—>—>Configuration—>ServerStart—>Arguments:(TextArea).
  • Enter : -Xms256m -Xmx1024m and Save.

Oh, btw JRockit does not have any concept of PermSize.

Mani
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  • Thanks for the response reply helpful. So now how do I determine where the memory leak is occurring and why? How do I get the java dumb and garbage collection logs from a remote server ? – Sam Oct 23 '12 at 11:55
  • I would also suggest [JRockit Mission Control](http://docs.oracle.com/cd/E13150_01/jrockit_jvm/jrockit/tools/index.html). If you are facing issues while using the tool, close this question by selecting one as an answer and open a new post with the mission tool issue with all the error details. – Mani Oct 23 '12 at 16:16
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Get basic knowledge of the JVM parameters.

Simply setting a couple of JVM memory parameters to higher values won't help but only move the error into the future. You have to analyze the application to find out the real problem. JRockit comes with a very good memory analyzing tool Mission Control. Watch the demo, which will help to find out which part of your application causes the Out Of Memory error.

Mani
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Timo Hahn
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  • Thanks for the response i tried connecting mission control to the remote server but it is unable to connect evemn after providing the Xmanagement:ssl=false,authenticate=false,port=7099 Djava.rmi.server.hostname=hostAddress(where weblogic is located). Any idea? – Sam Oct 23 '12 at 11:58