Real-time database consist of data processing control for a system of heavy work load and traffic that is constantly and rapidly changing or performing updates. A real-time transaction is processed at a rapid level therefore, the database can receive speedy result to be acted on or read for an update or information retrieval. An example of this would be a stock market; the currency amounts and index numbers are constantly changing. The use of real-time database systems is emerging in many applications such as, industrial process control systems, multi-media systems and many critical data access application. Real-time databases are well suited for use in banking, reservation systems, air traffic control systems, shipping tracking, online bidding systems, and more. More in depth, an air-traffic control systems constantly monitor hundreds of aircrafts and makes decisions about incoming flight paths and determines the order in which aircrafts should land based on data such as fuel, altitude, and speed. If any of this information is late, the result could be devastating. It is possible that these systems consist of a single-type or multiple-types of real-time transactions, or even mixed with non-real-time transactions. However, non-real-time are classified as traditional database transactions (contains persistent data this is not affected by time).
In such systems, real-time databases have time constraints. They are characterized by stern deadlines and high reliability requirements. A critical transaction in a real-time database is characterized by computation time and a completion deadline. There are three different types of deadlines: hard, soft and firm. Each deadline is measured against a value (a certain range for which the data is valid) versus time deadline. See figure 1 below. A hard deadline, requires that each data packet reach its destination before the packet has expired otherwise, the process could be lost and cause a possible problem. A Soft deadline meets as many deadlines as possible and last a firm deadline measure how important it is to complete the transaction at some point after the data packet/s arrive at their destination.These systems must have predictable response times and process various kinds of data in a timely fashion for success.
Real-time database systems must have predictable response times and process various kinds of data in a timely fashion for success. These database systems offer a way of monitoring a physical system and permitting real time data streams to be output to a database. A traditional system, is persistent and accurate, but does not have the capability to handle constant changing data.