Oracle Real Application Clusters (RAC) allows a single Oracle database to run on multiple servers to maximize availability and enable horizontal scalability while accessing shared storage. User sessions connected to Oracle RAC instances can failover and safely replay changes during outages without any changes to end-user applications, so users are not affected by interruptions.
Oracle Real Clusters and Enterprises
Oracle Real Application Clusters provides a foundation for Oracle's Enterprise Grid Computing architecture. Oracle RAC technology allows the use of a low-cost hardware platform to achieve the highest levels of quality of service, which can compete with and even exceed the levels of availability and scalability achieved by high-cost SMP mainframes.
Thanks to reduced administrative costs and the provision of new levels of manageability flexibility, Oracle makes the enterprise grid environment possible. Oracle RAC 11g Release 2 enables customers to build a dynamic grid infrastructure for their respective businesses.
What is Oracle Clusters Really?
Oracle Real Application Clusters is an option of Oracle Database first introduced with Oracle 9i. Today, Oracle Real Application Clusters constitutes a proven technology used by thousands of customers across various applications and industries. Oracle RAC offers different options to scale applications beyond the capabilities of a single server.
In this way, customers take advantage of lower-cost generic hardware to reduce total ownership costs and obtain a scalable computing environment that supports application workloads. Oracle RAC allows Oracle Database to run all types of clustered applications in a mainframe environment, including widely used packaged products (such as Oracle Applications, Peoplesoft, SAP) and custom-developed applications that may be OLTP, DSS, or mixed workload.
Oracle Real Application Clusters is a key component of Oracle's high availability architecture, which provides guidelines for designing the highest levels of availability for applications. Oracle RAC provides the capability to eliminate the server as the single point of failure in any database application environment.
What is the Architecture of Oracle Real Clusters?
Oracle RAC databases are clustered databases. The cluster is a group of independent servers that work together as a single system. Clusters offer greater fault tolerance and incremental modular growth of the system in single symmetric multiprocessing (SMP) systems.
In the event of a system failure, clustering ensures that users continue to enjoy high availability and do not lose access to critical information. Redundant hardware components, such as interconnections, disks, and additional nodes, enable the cluster to provide a high level of availability. Such redundant hardware architectures eliminate single points of failure and offer exceptional fault tolerance capabilities.
Through Oracle Real Application Clusters, the Oracle instance (the execution of memory structures and processes on a server to allow access to information) is separated from the Oracle database (the physical structures stored that actually contain the information, commonly referred to as "data files").
The clustered database is a single database that can be accessed by multiple instances. Each instance runs on an individual server in the cluster. When additional resources are needed, more nodes and instances can be added to the cluster without causing downtime.
Once the new instance is started, applications that use services can take advantage of it immediately, without any changes to the application or application server.
What are Its Main Features?
Cache Synchronization
Application developers can connect to any database instance in the cluster without making any changes to the application, reducing downtime.
Intelligent Cluster Reconfiguration
Customers reduce the impact of service disruptions by automatically redirecting connections to surviving instances.
Complete Package Protection
Oracle RAC provides end-to-end protection for customer databases by safely replaying transactions during outages without affecting the end-user experience.
What are the Main Benefits of Oracle Real Clusters?
Reliability
Oracle Database is renowned for its reliability. Oracle Real Application Clusters enhances this feature even further by eliminating the database server as a single point of failure. If one instance fails, the other instances in the cluster remain open and active. Oracle Clusterware monitors Oracle processes and immediately restarts any failed component.
Recovery Capability
Oracle Database includes various features to recover from all types of failures more easily. If an instance fails in an Oracle RAC database, any other instance in the cluster recognizes it, and recovery occurs automatically. Fast Application Notification, Fast Connection Failover, and Transparent Application Failover enable applications to easily mask component failures so that users do not perceive them.
High Availability
Oracle Real Application Clusters provides the necessary infrastructure for achieving high availability in data centers. It is also an integral part of Oracle's high availability architecture, providing best practices for delivering the best data management solutions. Oracle Real Application Clusters protects the main features of high availability solutions.
Continuous Operations
Oracle Real Application Clusters offers continuous service in the event of failures, whether scheduled or unscheduled. If a node (or instance) fails, the database remains open, and the application can access the data. Most database maintenance operations can be completed without any downtime and are transparent to the user. Many other maintenance tasks can be performed individually to eliminate or minimize downtime. Fast Application Notification and Fast Connection Failover help applications meet service levels and mask cluster component failures.
Fault Detection
Oracle Clusterware automatically monitors Oracle RAC databases and other Oracle processes (ASM, reception, etc.) and enables quick problem detection in the environment. Additionally, it allows for rapid recovery before anyone notices that a failure has occurred. With Fast Application Notification, applications receive immediate notification of cluster component failures and mask the failure from the user's perspective by forwarding the transaction to a surviving node in the group.
Scalability
Oracle Real Application Clusters offers a unique technology for scaling applications. Traditionally, when a database server lacked more capacity, it was replaced with a larger new server. The more capacity servers have, the more expensive they are. In the case of databases using Oracle RAC, there are alternatives for increasing capacity.
Applications that traditionally run on SMP servers can be migrated to use smaller server clusters. Another option is to maintain the existing hardware that has been invested in and add a new server to the cluster (or create a cluster) to increase capacity.
Adding servers to a cluster with Oracle Clusterware and Oracle RAC does not cause an interruption, and as soon as the new instance is started, the application can benefit from the additional capacity. All servers in the cluster must run the same operating system and the same version of Oracle, but they do not need to have the same capacity.
Currently, customers use clusters that meet their needs, ranging from server clusters where each server is a 2-CPU secondary server to clusters where each server has 32 or 64 CPUs.
Availability and Scalability as Goals
Oracle Real Application Clusters was designed to provide high availability and scalability. With protection against hardware and software failures, Oracle Real Application Clusters offers high system availability and ensures constant access to data. The features of vertical scalability and horizontal scalability provide a platform capable of growing in any direction, facilitating business growth for companies.
Both existing and newly developed applications benefit from the transparency that Oracle Real Application Clusters provides. This simplifies application development, management, and change management while reducing total ownership costs.
Oracle Real Application Clusters is unique in the market for both its solutions and capabilities. Thousands of customers worldwide use Oracle RAC in mission-critical applications and in many other application environments across all sectors.
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