+ be sure that hot-deployment is turned ON for app server
+ start portal; check for log message similar to this one:
+ deploy some sample plugin, and check that it was deployed correctly (try to add test portlet to a page).
+ undeploy the sample plugin
+ disable hot-deployment on app server. sometimes you need to restart the server.
+ start the portal again, log messages will say that hot deployment is not supported:
+ deploy sample plugin - it will not be deployed. There will be message in the log Deployment will start in a few seconds., but nothing will happened.