How to Increase your Java Heap size with CA Web Viewer 12.1

Document ID : KB000009663
Last Modified Date : 21/09/2018
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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 


Apache Tomcat


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? 

Where to find and change these settings:
Web Viewer for Windows with Tomcat running as a Windows Service:
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 4096    (or up to 8192) 
Save and close the file.
Enter the following command: service.bat install 

Web Viewer for Windows with Tomcat not running as a windows service:
In apache-tomcat/bin/catalina.bat:

             set "CATALINA_OPTS=-Xms1024m and Xmx2048m...

•Web Viewer for Windows with Tomcat running as Windows service:  In apache-tomcatxxxx\bin\service.bat (for example):

      find "--JvmMs1024


Other Operating Systems:
In apache-tomcat/bin/ 
     CATALINA_OPTS="-Xms1024m –Xmx2048m…" 

Running Tomcat as a started task,
he Java Heap size change will be either in you STDENV options, or the JCL, wherever your relevant definition is for:
IBM_JAVA_OPTIONS = -Xms256m -Xmx1024m
As noted below, the minimum recommendation for this setting is for:
IBM_JAVA_OPTIONS = -Xms1024m -Xmx4096m
..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. If it ends up being at 2048m or lower, you should ask the System Administrators for more to be allocated if possible. 

What Amount to Specify
The amount of memory you specify for the maximum value is dependent on the amount of memory you have available.

  • Xmx4096m is the minimum recommended, and in cases of heavy usage, you may need to increase that to Xmx8192m.

You do not need to change the initial heap size setting even if it is lower than the value above.   


Additional Information:

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.