Much of the monitoring you'll do is related to job requests, where Oracle Enterprise Scheduler work is done. You can get a snapshot of recent work done as job requests, including the load those requests are placing on the system. You can also view the status of current and pending requests.
For an Oracle Enterprise Scheduler instance, you can find out how it is performing currently and how it has performed historically.
You can get the status of a service instance, as well as service components such as the request dispatcher and processor.
Finally, you can get log information about job requests and Oracle Enterprise Scheduler.
Use Fusion Middleware Control to do most of the monitoring you'll need. Its user interface provides data about system performance in both graphical and tabular form.