Routing overflow
Beginner
How many more wires want to pass through a spot than there are lanes for.
Novice
How many more wires want to cross a GCell border than it has free tracks for. A report gives it per layer, as a total and as the worst single border. Zero overflow everywhere means the global plan fits.
Expert
Total overflow sums the excess over every border; maximum overflow shows the worst one. Small, scattered overflow often clears in detailed routing. Overflow clustered near large blocks or dense cells usually becomes rule violations and needs a placement or floorplan fix.
Explained in Routing (Design Flow).
See also: Congestion, GCell (global routing cell).