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
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.
Oracle RAC allows multiple computers to run Oracle RDBMS
software simultaneously while accessing a single database
, thus providing a cluster
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.
Oracle RAC depends on the infrastructure
component Oracle Clusterware
to coordinate multiple servers and their sharing of data storage.
Prior to Oracle 9, network-clustered Oracle databases used a storage device as the data-transfer medium (meaning that... Read More