Most connections offer a Hold files property. If this property is enabled, jobs are not allowed to move through the connection. This is mostly used to temporarily hold jobs (for example because there is a problem with a process downstream).
The canvas displays connections on hold as an orange dashed line (see examples below).
Although editing in the Properties pane is disabled while a flow is active (see activating and deactivating flows), the status of the Hold files property can be modified at any time through the context menu of the connection.