Oracle RAC

In database computing, Oracle Real Application Clusters (RAC) — an option for the Oracle Database software produced by Oracle Corporation and introduced in 2001 with Oracle9i — provides software for clustering and high availability in Oracle database environments. Oracle Corporation includes RAC with the Standard Edition of Oracle Database (aka Baby RAC), but makes it an extra-charge option for the Enterprise Edition.

Functionality

Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing a cluster database.

In a non-RAC Oracle database, a single instance accesses a single database. The database consists of a collection of data files, control files, and redo logs located on disk. The instance comprises the collection of Oracle-related memory and operating system processes that run on a computer system.

In an Oracle RAC environment, two or more computers (each with an instance) concurrently access a single database. This allows an application or user to connect to either computer and have access to a single coordinated set of data.

Aims

Implementation

Oracle RAC depends on the infrastructure component Oracle Clusterware to coordinate multiple servers and their sharing of data storage.

Cache Fusion

Prior to Oracle 9, network-clustered Oracle databases used a storage device as the data-transfer medium (meaning that...
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