The primary function of a Junction symbol is to supply the flow logic of the process described in the IDEF3 Process Flow diagrams. When you draw line junctions in System Architect, the system determines whether the junction is a “fan in” or “fan out” junction.
Synchronicity
Synchronicity determines whether all previous "Fan In" or subsequent "Fan Out" processes all complete before accepting new objects. The System Architect Simulator controls synchronicity by changing the size of the "Buffer" that holds objects either before or after processing objects in a Process UOB.