Configure your Java Virtual Machine

Navigate to Servers > Server Types > WebSphere application servers;
Select the appropriate server from the list i.e WebSphere_Portal;
In the Server Infrastructure section expand Java and Process Management;
Select the Process definition link;
In the Additional Properties section Select the Java Virtual Machine link;
Set the fields as follows:
Initial heap size :512

Maximum heap size :1024

Click Apply to set the values;
In the Additional Properties section Select the Custom Properties link;
Click New and set the properties as follows:
Name : com.ibm.websphere.security.util.authCacheCustomKeySupport

Value : false

Click OK to add the property;
The following step is only required on non-Windows platforms.
Click New and set the properties as follows:

Name : java.awt.headless

Value : true

Click OK to add the property;
Save the changes made to the master configuration using the Save option as before.