How to set java heap size in Apache Ant?

Set environment variable ANT_OPTS. Look at the file $ANT_HOME/bin/ant or \bin\ant.bat, for how this variable is used by Ant runtime.

set ANT_OPTS="-Xms512m -Xmx512m"  (Windows)
export ANT_OPTS="-Xms512m -Xmx512m"  (ksh/bash)
setenv ANT_OPTS "-Xms512m -Xmx512m"  (tcsh/csh)

How to set java heap size in Tomcat?

Stop Tomcat server, set environment variable CATALINA_OPTS, and then restart Tomcat. Look at the file tomcat-install/bin/catalina.sh or catalina.bat for how this variable is used. For example,

set CATALINA_OPTS=-Xms512m -Xmx512m  (Windows, no "" around the value)
export CATALINA_OPTS="-Xms512m -Xmx512m"  (ksh/bash, "" around the value)
setenv CATALINA_OPTS "-Xms512m -Xmx512m"  (tcsh/csh, "" around the value)

In catalina.bat or catallina.sh, you may have noticed CATALINA_OPTS, JAVA_OPTS, or both can be used to specify Tomcat JVM options. What is the difference between CATALINA_OPTS and JAVA_OPTS? The name CATALINA_OPTS is specific for Tomcat servlet container, whereas JAVA_OPTS may be used by other java applications (e.g., JBoss). Since environment variables are shared by all applications, we don't want Tomcat to inadvertently pick up the JVM options intended for other apps. I prefer to use CATALINA_OPTS.

How to set java heap size in JavaEE SDK/J2EE SDK/Glassfish/Sun Java System Application Server?

Stop the application server, edit $GLASSFISH_HOME/domains/domain1/config/domain.xml, search for XML element name java-config and jvm-options. For example,

<java-config suffix="...">
<jvm-options>-Xmx512m</jvm-options>
<jvm-options>-XX:NewRatio=2</jvm-options>
<jvm-options>-XX:MaxPermSize=128m</jvm-options>
...</java-config>

You can also change these settings in the web-based admin console, typically at http://localhost:4848/, or https://localhost:4848/. Go to Application Server near the top of the left panel, and then on the right panel, click JVM Settings -> JVM Options, and you will see a list of existing JVM options. You can add new ones and modify existing ones there.

Yet another option is to use its Command Line Interface (CLI) tool command, such as:

./asadmin help create-jvm-options
./asadmin help delete-jvm-options

They may be a bit hard to use manually, but are well suited for automated scripts.

Taken from here: http://javahowto.blogspot.com/2006/06/6-common-errors-in-setting-java-heap.html