Online transaction processing (OLTP) is a mode of processing that is characterized by short transactions recording business events and that normally requires high availability and consistent, short response times. This category of applications requires that a request for service be answered within a predictable period that approaches “real time.” Unlike traditional mainframe data processing, in which data is processed only at specific times, transaction processing puts terminals online, where they can update the database instantly to reflect changes as they occur. In other words, the data processing models the actual business in real time, and a transaction transforms this model from one business state to another. Tasks such as making reservations, scheduling and inventory control are especially complex; all the information must be current.