Oracle real application clusters enable users to construct scalable environments that run mission-critical business applications by combining smaller commodity servers into a cluster.
FREMONT, CA: A cluster is a collection of interconnected computers or servers that seem to end-users and applications as though they are one server. Oracle RAC (Oracle Real Application Clusters) allows one to cluster Oracle databases. Oracle RAC relies on Oracle Clusterware to connect multiple servers and make them work as a single system.
Oracle Clusterware is an Oracle database-integrated cluster management solution that is portable. Oracle Clusterware is also necessary for Oracle RAC to work. Oracle Clusterware also allows single-instance Oracle databases and Oracle RAC databases to use Oracle's high-availability infrastructure. One can use Oracle Clusterware to establish a clustered storage pool that can be utilized by any mix of single-instance and Oracle RAC databases.Oracle Clusterware is the only Clusterware one will need for most Oracle RAC platforms. If the Clusterware is endorsed for Oracle RAC, one can also utilize it from other vendors.
The Oracle database and the instance have a one-to-one relationship in single-instance Oracle databases. The database and instances in Oracle RAC settings, on the other hand, have a one-to-many connection. An Oracle RAC database can contain up to 100 instances that all connect to the same database. The same interconnect must be utilized by all database instances, which Oracle Clusterware can also use.
The architecture of Oracle RAC databases differs from single-instance Oracle databases in that each Oracle RAC database instance also has:
• For each instance, at least one additional redo thread is required.
• An instance-specific undo tablespace.
The processing capacity of numerous servers together can give better throughput and Oracle RAC scalability than a single server.
An Oracle RAC setup is typically housed in a single data center. One can, however, configure Oracle RAC on an expanded distance cluster, which is an architecture that enables all nodes at all sites to execute transactions as part of a single database cluster actively and offers speedy recovery from a site failure. The cluster's nodes are located in two buildings that are separated by considerable distances in an extended distance cluster (from across the street, across a campus, or a city). The data should be located at both sites for reasons of availability, necessitating the use of disk mirroring technology for storage.
Oracle RAC is a unique technology that delivers high availability and scalability for all sorts of applications. Oracle's RAC infrastructure is also essential for executing Oracle's corporate grid computing architecture. The server is not a single point of failure because several instances access the same database. Oracle RAC enables users to construct scalable environments that run mission-critical business applications by combining smaller commodity servers into a cluster. Applications deployed on Oracle RAC databases can run without requiring any code changes.