After an installation, the agent log in <agent_home>/logs will contain this message:

Started AppDynamics Java Agent Successfully

If the agent log file is not present, the Java Agent may not be accessing the javaagent command properties. To troubleshoot, check the application server log file where STDOUT is logged. It will have the fallback log messages, useful for troubleshooting the agent.

Also, verify that the agent is able to connect to the Controller in the Controller UI. To verify, log in to the Controller UI and click the Settings icon at the top right of the page, and then Agent Management > Manage Agents. In the list, search for the agent by machine hostname.