When you try to deploy your portlets to clustered environment and you get the following error message:
To target shared library to the cluster you can do this by using the WLS Administration Console. You select the shared library from the deployment and then from the tabs select the target, there you can then select the cluster target or managed servers.
Which libraries are needed or used by standard JSR-286 Portlet developed with JDeveloper:
Of course you may need also another libraries depending you which technology scopes you used when you develop your portlet application. The above libraries are the minimum for the standard JSR-286 Portlet.