JMX framework can enhance the manageability of your application by
1. Monitoring your application for critical events, performance problems, and error condition statistics. E.g: you may be notified, if there are sudden increases in traffic or sudden drop in performance of your website.
2. Creating your application more configurable and controllable at runtime by directly exposing application API and parameters. e.g: you could switch your database connection to an alternate server or a different server. You may also modify the level of debugging and logging within the application without halting the server. You could write a poller, which rolls your database at a regular parts as a JMX sevice, so that you may change the polling interval, stop and start the poller through your console without having to halt the server.
3. By interfacing JMX to your database server, hardware and application server, health checks may be executed of your infrastructure.