Setting the JVM arguments of the Websphere servers can be done through the Administration Console by performing the following steps:
1. Expand from the left Menu “Servers” and select the WAS Server from the list.
2. From the “Server Infrastructure” list, expand the “Java and Process Management” option and click on Process Definition.
3. In the Process Definition screen, select the “Java Virtual Machine”.
4. Once in the Java Virtual Machine screen enter the appropriate settings for the server JVM as shown by the following screen:
Changes in the JVM settings will be active next time you will boot WAS.