This book is about the different types of database management systems and security issues of databases and networks. We will take the Oracle database to elaborate with a detailed discussion on the base of RDBMS and other databases like NoSql, Mobile database, and open-source database. Oracle has transformed the landscape of data management to a very high standard. By itself, Oracle uses database tables to store any structured and unstructured data. However, it also stored a set of codes with business logic in the form of a trigger, procedure, function, etc. While this is a unique advantage, this approach is highly adopted for the sake of efficiency. Oracle RDBMS does not compromise performance. With proper configuration and tuning it always extracts information and data with lightning speed.