It may help to define reference first. An SSIS Catalog Reference is a relationship between an SSIS Project and an SSIS Catalog Environment in the SSIS Catalog. One or more references to environments may be configured for a project. At execution time one and only one reference may be selected – like Highlander, “There can be only one.”
A broken reference occurs when one configures a reference between a project and an environment, and then the environment is deleted.
Read on to see what this looks like in the SSIS Catalog Browser and SISS Catalog Compare tools, as well as how you can prevent accidentally creating broken references.