This custom alert can be used to catch sessions that have been running for more than X seconds. The first columns provides a description of the session and what the session is doing, and the 2nd column is the time it has been running.
Configure a Custom SQL Alert - Multiple Numeric Return alert in DPA, and plug in the attached query for the SQL Statement field. Setup thresholds based on the number of seconds you consider a long running query. Here is an example I am using to catch session running longer than 5 minutes (300 seconds):
