JAVA_OPTS Variable Details

Memory Available to the Java JVM

Increasing the memory available to the Java JVM

JAVA_OPTS="-Xmx1024m -Xms256m"

export JAVA_OPT

Options description:

-Xmx sets the maximum amount of memory that can be allocated to the JVM heap; here it is being set to 1024 megabytes.

-Xms sets the initial amount of memory allocated to the JVM heap; here it is being set to 256 megabytes.

Run Java JVM in Server Mode

The Java JVM can optimize a number of things for server environments. You can explicitly select the Java HotSpot Server VM with the -server option.

JAVA_OPTS="-Xmx1024m -Xms256m -server"

export JAVA_OPT


What the option means:

-server instructs the launcher to use the Java HotSpot Server VM.



PermGen Memory

If you start getting java.lang.OutOfMemoryError: PermGen space error messages. You may want to include a "-XX:MaxPermSize" option in your JAVA_OPTS.


JAVA_OPTS="-Xmx1024m -Xms256m -server -XX:MaxPermSize=128m"

export JAVA_OPT

What the option means:

-XX:MaxPermSize set the maximum amount of memory that can be used for PermGen.

Summery :

You can increase heap memory available to the JVM.

You can open remote monitoring ports so that Jconsole on another system can watch how your Tomcat is running.

You can add in a -server to switch from the client (quicker start, slower running) JVM to the server (slower starting, quicker running) JVM.

You can increase java thread stack size using the -Xss option (same way to specify amount of memory as in -Xms and -Xmx as described in the "increase heap memory".


Enjoy !!!!!!