9.5 About JVM Arguments

The memory arguments defined in the domain.conf.bat file are applicable to the processes of domain controller and process controller. Ensure that you set these memory arguments on each node of the cluster.

In a managed domain, the JVM settings are declared in the host.xml and the domain.xml configuration files. Domain controller components responsible for starting and stopping server processes use these settings. In a standalone server instance, the server startup processes can pass command line settings at startup. These settings can be declared from the command line or from the System Properties screen in the Management Console.

Managed Domain

An important feature of the managed domain is the ability to define JVM settings at multiple levels. You can configure custom JVM settings at the host level, by server group, or by server instance. The more specialized child elements override the parent configuration, allowing for the declaration of specific server configurations without requiring exclusions at the group or host level. This also allows the parent configuration to be inherited by the other levels until settings are either declared in the configuration files or passed at runtime.

JVM settings in the domain configuration file

The following example shows a JVM declaration for a server group in the domain_db.xml configuration file.

<server-group name="main-server-group" profile="default"> 
<jvm name="default"> 
<heap size="64m " max-size="512m "/> 
</jvm > 
<socket-binding-group ref="standard-sockets"/> 

In this instance a server group called main-server-group declares a heap size of 64 megabytes, and a maximum heap size of 512 megabytes. Any server that belongs to this group inherits these settings. You can change these settings for the group as a whole, by the host, or the individual server.

The following example shows a JVM declaration for a server group in the host.xml configuration file.

<server name="server-one" group="main-server-group" auto-start="true"> 
<jvm name="default"> 
<heap size="64m " max-size="256m "/> 
</jvm > 

In this instance, a server named server-one belongs to the server group named main-servergroup, inheriting the JVM settings from the default JVM group. In the previous example, the main heap size for main-server-group was set at 512 megabytes. By declaring the lower maximum heap size of 256 megabytes, server-one can override the domain.xml settings to fine-tune performance to the required levels.

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