Effect on channel busy
Packet switching reduces path busy by elimination of “dead” time
Increased data rate further reduces path busy by ratio of effective transfer rates (4.5:1, or 9:1 for express)
Bi-directional transfer further reduces by ratio of least predominant transfer type to total (2:1 r/w reduces by 1/3, 1:1 by 1/2)
But: FICON introduces 10-13% overhead busy