Configure the Java virtual machine

Use wsadmin.sh to configure settings for a JVM. As part of configuring an application server, you might define settings that enhance the way the operating system uses of the Java virtual machine.

There are three ways to perform this task. Use the steps in this topic to use the setJVMDebugMode command for the AdminTask object or the AdminConfig object to modify the JVM configuration. Alternatively, we can use the configureJavaVirtualMachine Jython script in the AdminServerManagement script library to enable, disable, or configure the debug mode for the JVM. The wsadmin tool automatically loads the script when the tool starts. Use the following syntax to configure JVM settings using the configureJavaVirtualMachine script:

AdminServerManagement.configureJavaVirtualMachine(nodeName, serverName, debugMode, debugArgs, otherAttributeList)

For additional information and argument definitions, see the documentation for the AdminServerMananagment script library.

The JVM is an interpretive computing engine responsible for running the byte codes in a compiled Java program. The JVM translates the Java byte codes into the native instructions of the host machine. The application server, being a Java process, requires a JVM in order to run, and to support the Java applications running on it. JVM settings are part of an application server configuration.

1. Start the wsadmin scripting tool.
   

2. There are two ways to complete this step. We can use the setJVMDebugMode command for the AdminTask object or the AdminConfig object to modify the JVM configuration. Choose one of the following configuration methods:

   • Use the AdminTask object:

     • Jacl:
       $AdminTask setJVMDebugMode {-serverName server1 -nodeName node1 -debugMode true}

     • Jython:
       AdminTask.setJVMDebugMode (['-serverName', 'server1', '-nodeName', 'node1', '-debugMode', 'true'])

   • Use the AdminConfig object:

     1. Identify the server and assign it to the server1 variable:

        • Jacl:
          set server1 [$AdminConfig getid /Cell:mycell/Node:mynode/Server:server1/]

        • Jython:

          server1 = AdminConfig.getid('/Cell:mycell/Node:mynode/Server:server1/')
          print server1

        Example output:

        server1(cells/mycell/nodes/mynode/servers/server1|server.xml#Server_1)

     2. Identify the JVM that belongs to the server of interest and assign it to the jvm variable:

        • Jacl:
          set jvm [$AdminConfig list JavaVirtualMachine $server1]

        • Jython:

          jvm = AdminConfig.list('JavaVirtualMachine', server1)
          print jvm

        Example output:

        (cells/mycell/nodes/mynode/servers/server1:server.xml#JavaVirtualMachine_1)

        (zos)

        (cells/mycell/nodes/mynode/servers/server1:server.xml#JavaVirtualMachine_1)
        (cells/mycell/nodes/mynode/servers/server1:server.xml#JavaVirtualMachine_2)

     3. (zos) Identify the controller JVM of the server and its servant region JVM:

        • Jacl:

          set cjvm [lindex $jvm 0]
          set sjvm [lindex $jvm 1]

        • Jython:

          # get line separator
          import java
          lineSeparator = java.lang.System.getProperty('line.separator')
          arrayJVMs = jvm.split(lineSeparator)
          cjvm = arrayJVMs[0]
          sjvm = arrayJVMs[1]

     4. Modify the JVM to enable debugging:

        • Jacl:
          (dist)(iseries)
          $AdminConfig modify $jvm {{debugMode true} {debugArgs "-Djava.compiler=NONE -Xdebug -Xnoagent -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=7777"}}

          
          (zos)

          $AdminConfig modify $cjvm {{debugMode true} {debugArgs "-Djava.compiler=NONE -Xdebug -Xnoagent  -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=7777"}}
          $AdminConfig modify $sjvm {{debugMode true} {debugArgs "-Djava.compiler=NONE -Xdebug -Xnoagent  -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=7777"}}

        • Jython:
          (dist)(iseries)
          AdminConfig.modify(jvm, [['debugMode', 'true'], ['debugArgs', "-Djava.compiler=NONE -Xdebug -Xnoagent -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=7777"]])

          
          (zos)

          AdminConfig.modify(cjvm, [['debugMode', 'true'], ['debugArgs', "-Djava.compiler=NONE -Xdebug  -Xnoagent -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=7777"]])
          AdminConfig.modify(sjvm, [['debugMode', 'true'], ['debugArgs', "-Djava.compiler=NONE -Xdebug  -Xnoagent -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=7777"]])

3. Save the configuration changes.

   Use the following command example to save the configuration changes:

   AdminConfig.save()

4. In a network deployment environment only, synchronize the node.

   Use the syncActiveNode or syncNode scripts in the AdminNodeManagement script library to propagate the configuration changes to node or nodes.

   • Use the syncActiveNodes script to propagate the changes to each node in the cell:
     AdminNodeManagement.syncActiveNodes()

   • Use the syncNode script to propagate the changes to a specific node:
     AdminNodeManagement.syncNode("myNode")

Related tasks

Configure the JVM

Automating server administration

Node administration scripts

Server settings configuration scripts

Commands for the AdminConfig object