Possible symptoms requiring an increase in Java Heap size
These parameters specify the Memory settings (Java heap size) when launching Tomcat
ms – the initial heap size when the Java application is starting
mx – the maximum heap size
If you are on a Windows server, before you change these settings, check these hardware recommendations for Windows server to make sure that you have enough RAM:
KB000091893 What are 12.1 Web Viewer and Windows Server Hardware requirements? In general, you can use about 50% of your installed memory (RAM) for heap if no other applications are running on your server.
What Amount to Specify
The amount of memory you specify for the maximum value is dependent on the amount of memory you have available.
If it ends up being at 2048m or lower, you should ask the System Administrators for more RAM to be allocated.
Stop the Tomcat service.
On the command line, go to the <installation dir>/tomcat/bin directory.
Enter the following command: service.bat remove
Open the <installation dir>/tomcat/bin/service.bat file in a text editor.
Locate the following entries and change the numbers to suitable memory values (in MB):
--JvmMs 512
--JvmMx 1024
Save and close the file.
Enter the following command: service.bat install
In apache-tomcat/bin/catalina.bat find:
set "CATALINA_OPTS=-Xms1024m and Xmx2048m...
Update and save and close the file.
In catalina.sh, set In apache-tomcat/bin/catalina.sh find:
CATALINA_OPTS="-Xms1024m –Xmx2048m…" and update and save and close the file.
The Java Heap size will be either in your STDENV (parameter) options, or the JCL, wherever your relevant definition is for:
IBM_JAVA_OPTIONS = -Xms256m -Xmx1024m
Update and save.
..but if the System does not have that much available, you will get a startup error that notes the Java Heap size nnnnm could not be allocated. If that happens you should lower the -Xmx setting by 512m at a time until the System accepts that setting.
For Windows, Unix and Linux, monitor the catalina.out file for java.lang.OutOfMemoryError: Java heap space errors to be sure that the setting you specified provides enough heap space.