A join failure occurs in a join step or gateway step when the Process Engine determines that one of the expected inputs to the step is an incomplete transition (or dead path) and the join step or gateway cannot be satisfied, as described in How Incomplete Transitions Affect Join Steps and Gateways, above. In this case, you can specify an Unsatisfied Join transition type for the step, providing a processing path to a downstream step that can take additional actions when the a step experiences a join failure.