Have you had a collection job fail with a status of "Aborted (Circuit Breaker)" and all you did was kick of the collection again with "Ignore Circuit Breaker"?
The Circuit Breaker is there to protect you. In the past customers have had issues with their source data being incorrect and then that incorrect data being pulled into the system. For example, some collections are collected from CSV files that the customer builds with some manual or automatic process from various systems within their organization. If this aggregation process fails, or does not properly create the CSV files, then our collectors will gather the incorrect data and attempt to process it, typically resulting in cases where we think a significant number of objects or relationships have been deleted, which in turn can trigger all kinds of actions. The Circuit Breaker can prevent that. It raises a red flag that a particular collection has too much change, and gives the administrator a chance to review the raw data before we take it on board.
The Circuit Breaker is designed to stop a collection process that exceeds a percentage of change. That change could be something New, Missing or Changed, and it pertains to objects and direct entitlements. Our OOTB percentage change is 5%, but that can be adjusted. We allow the percentage to be changed system wide or it can be changed on a per collector basis as well as on the type of change that occurs. So if you know that your Ldap server does not have a lot of activity you can keep the OOTB percentage. If you have self-service HR system where the users are constantly making modifications to their information you may want to increase the percentage for that collector.
In the Collector's Guide there is a section on "Configuring a Data Processing Interruption Threshold" which will give you more information on how to adjust the setting.