Although centralized networks provide benefits in some situations, the single centralized computer approach creates severe drawbacks. It causes the network to be inflexible. Also, very complicated and costly system software is needed to move application programs in and out of their on-line library, to assign priorities to messages, to move data throughout the network, and so on. The network is quite vulnerable to disaster, since it is dependent on the functioning of a single central computer. Finally, a centralized network may not be responsive to the needs of users at the various remote points.