Improved availability:The data in a distributed system may be replicated so that it is at more than one site. Thus, the failure of a node or a communication link does not necessarily make the data inaccessible. The skill of most of the systems to continue to operate despite the failure of one site results in enhanced availability which is vital for database systems used for real-time applications. For instance, loss of access to data in an airline might result in the loss of potential ticket buyers to competitors.