Understanding the Oracle Database 18c Technical Architecture An Oracle Database consists of at least one database instance and one database. The database instance handles memory and processes. The database consists of physical files called data files, and can be a non-container database or a multi-tenant container database. An Oracle Database also uses several database system files during its operation. A single-instance database architecture consists of one database instance and one database. A one-to-one relationship exists between the database and the database instance. Multiple single-instance databases can be installed on the same server machine. There are separate database instances for each database. This configuration is useful to run different versions of Oracle Database on the same machine. An Oracle Real Application Clusters (Oracle RAC) database architecture consists of multiple instances that run on separate server machines. All of them share the same database. ...