Business Continuity and High Availability Of Oracle RAC

Oracle Real Application Clusters (RAC) is the foundation for data center high availability (HA). Based on Oracle Grid Infrastructure as its management framework that provides the means for planned and unplanned as well as runtime and capacity-on-demand management the Oracle RAC Stack ensures uninterrupted data center operations for applications of any kind.

Oracle RAC is an integral component of Oracle’s Maximum Availability Architecture, which provides best practices to provide the highest availability for your data center. In this context, one of the key advantages of Oracle RAC is the inherent fault tolerance provided by multiple physical servers used by the database. Since the servers in the cluster run independently, the failure of one or more serversdoes not affect others. This architecture also allows a group of servers to be transparently put online or offline, while the rest of the system continues to provide uninterrupted database services.

Oracle RAC

Oracle RAC provides the following key characteristics, essential for HA data management:

·         Reliability – The Oracle Database is known for its reliability. Oracle RAC takes this a step further by removing the database server as a single point of failure. If an instance fails, the remaining instances in the cluster remain open and active. Oracle Clusterware monitors all Oracle processes and immediately restarts any failed component.

·         Error Detection – Oracle Clusterware automatically monitors Oracle RAC databases as well as other Oracle processes (Oracle ASM, instances, Listeners, etc.) and provides fast detection of problems in the environment. It also automatically recovers from failures often before users notice that a failure has occurred.

·         Recoverability – The Oracle Database includes many features that make it easy to recover from various types of failures. If an instance fails in an Oracle RAC database, it is recognized by another instance in the cluster and recovery will start automatically. Fast Application Notification (FAN) and Fast Connection Failover (FCF) and especially the Oracle RAC 12c Application Continuity feature make it easy to mask any component failure from the user.

·         Continuous Operations – Oracle RAC provides continuous service for both planned and unplanned outages. If a server (or an instance) fails, the database remains open and applications continue to be able to access data, allowing for business critical workloads to finish, mostly without a delay in service delivery.

             Most database maintenance operations can be completed without downtime and are transparent to the user. Many maintenance tasks can be performed in a rolling fashion so application downtime is minimized or eliminated.

New In Oracle Database 12c

New with Oracle Database 12c is the ability to contribute to the success of your business by
ensuring that business critical applications continue to operate despite failures on system level.

Application Continuity (AC) is a new technology that protects applications from instance and session failures by re-playing affected “in-flight” transactions on another database instance. Application Continuity uses the new Oracle Database 12c Transaction Guard feature that ensures that applications always get a “known result” (expected result) back from the database despite a failure on the database level or user induced “misoperation” such as using a double-click on purchase or the browser’s “back button” while checking out on a web-based order application. Such operations could otherwise result in unexpected outcome. Application Continuity requires certain Oracle Database 12c client access driver, while the Transaction Guard API can be used natively by various applications.
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