IBM 440 - Manual (Page 75)

Chapter 2. Positioning 61
– Implementing critical new solutions that may enable a competitive edge is
easier.
Reduced technical complexity
Three-tier logical architectures tend, in practice, to become five-tier
architectures (client, local server, central server, gateway, and enterprise
server). Server consolidation can simplify technical complexities by
eliminating the true number of tiers in a purported three-tier architecture by
reducing or eliminating central servers and gateways.