I have look at the documentation on the IBM site
Follow the steps stated
Using the JVM
As part of configuring an application server, you might define settings that enhance your system's use of the Java virtual machine (JVM).
To view and change the JVM configuration for an application server's process, use the Java Virtual Machine page of the console or use wsadmin to change the configuration through scripting.
Steps for this task
Access the Java Virtual Machine page.
Click Servers > Application Servers in the console navigation tree.
On the Application Server page, click on the name of the server whose JVM settings you want to configure.
On the settings page for the selected application server, click Process Definition.
On the Process Definition page, click Java Virtual Machine.
On the Java Virtual Machine page, specify values for the JVM settings as needed and click OK.
Click Save on the console taskbar.
Restart the application server.
I hope this helps
Adeyemi E Adegbile
Class loader settings
Use this page to configure a class loader for applications that reside on an application server.
To view this administrative console page, click Servers > Application Servers > server_name > Classloader >class_loader_ID.
States a string unique to the server identifying the class-loader instance. The product assigns the identifier. Data type String
Specifies the class-loader mode when the application class-loader policy is SINGLE. PARENT_FIRST causes the class loader to delegate the loading of classes to its parent class loader before attempting to load the class from its local classpath. PARENT_LAST causes the class loader to attempt to load classes from its local classpath before delegating the class loading to its parent; this allows an application class loader to override and provide its own version of a class that exists in the parent class loader. Data type String
Hope this helps
Adeyemi E Adegbile
Thank you so much for your reply. I have tried your suggestions but it didn't work (although I could do something wrong. I wonder if anyone did use AOP with Websphere). The reason it didn't work, as I understand is that WS is using it's own classloader which is hardcoded and not defined by -Djava.system.class.loader property. This is how WS controlles it's multiple classloader policies. AOP requires its classloader to be used instead of default classloader. Is there a way to force WS to use AOP classloader other than java.system.class.loader setting? I did check in runtime that all AOP settings are correct, WS seems to ignore it.