This custom alert will query the DBA_OBJECTS system table and return all materialized views that are currently invalid. This query could be modified to return any object or specific objects as needed.
The query will return the object information in the first column and a the number of minutes the object has been invalid in the second column. For the thresholds, use 1 as the min value, meaning anything that has been invalid more than 1 minute will cause the alert o be triggered. If you have have materialized views that become invalid but later will get revalidated, set the threshold to a higher value.
To add this to DPA, create a custom alert of type Custom SQL Alert - Multiple Numeric Return and make the alert look similar to below. For the SQL statement, past in the contents of the attachment:
