Provides seamless integration with, and migration to, Oracle Real Application Clusters (Oracle RAC) and Oracle Data Guard. In an Oracle cluster prior to version 12.1.0.2c, when a split brain problem occurs, the node with lowest node number survives. For more information, see Oracle Data Guard Concepts and Administration or the Oracle Streams Replication Administrator's Guide. A world-recognized e-commerce site uses multiple standby databasesa mix of both physical and logical databasesboth for disaster recovery and to scale out read performance by provisioning multiple logical standby databases using SQL Apply. Fast Recovery Area manages local recover-related files automatically. Oracle Enterprise Management support for Oracle ASM and Oracle ACFS, Grid Plug and Play, Cluster Resource Management, Oracle Clusterware and Oracle RAC Provisioning and patching, Figure 7-4 shows Oracle Database with Oracle RAC architecture. To ensure data consistency, each instance of a RAC database needs to keep heartbeat with the other instances. If the fast recovery area is on the source volume that is remotely mirrored, then you must also remotely mirror the flashback logs. See Section 7.1.3, "Oracle Database with Oracle RAC One Node" for more information. However, when you use Oracle Clusterware, there is no need or advantage to using third-party clusterware. With Database Server Grid and Database Storage Grid (described in Section 5.2 and Section 5.3), you can build standby database and testing hubs that use a pool of system resources. The following list describes some implementations for a multiple standby database architecture: Continuous and transparent disaster or high availability protection if an outage occurs at the primary database or the targeted standby database, Regional reporting or reader databases for better response time, Synchronous redo transport that transmits to a more local standby database, and asynchronous redo transport that transmits to a more remote standby database for optimum levels of performance and data protection, Transient logical standby databases (described in Section 3.6.3) for minimal downtime rolling upgrades, Test and development clones using snapshot standby databases (described in Section 3.6.4), Scaling the configuration by creating additional logical standby databases or snapshot standby databases. Footnote1Rolling upgrades with Oracle Clusterware and Oracle RAC incur zero downtime. Provides maximum protection from physical corruptions. Footnote1Recovery time indicated applies to database and existing connection failover. Split brain syndrome occurs when the instances in a RAC fails to connect or ping to each other via the private interconnect. Figure 7-3 Oracle Database with Oracle Clusterware (After Cold Cluster Failover). Dynamic Resource Provisioning allows for dynamic system changes. These figures show how you can use the Oracle Clusterware framework to make both Oracle Database and your custom applications highly available. In a split brain situation, voting disk will be used to determine which node(s) survive and which node(s) will be evicted. However, the online changes are not supported by SQL Apply or data capture, and therefore the effects of this subprogram are not visible on the logical standby database or replica database. Commonly, one will see messages similar to the followings in ocssd.log when split brain happens: Above messages indicate the communication from node 2 to node 1 is not working, hence node 2 only sees 1 node, but node 1 is working fine and it can see two nodes in the cluster. But 1 and 2 cannot talk to 3, and vice versa. What is Voting Disk & Split Brain Syndrome in RAC You might choose to use Oracle GoldenGate to configure and maintain a logical copy of your production database. To maintain the standby site for failover, not only must the standby site contain homogeneous installations and applications, data and configurations must also be synchronized constantly from the production site to the standby site. Figure 7-1 Single-Node, Nonclustered Oracle Database with an Oracle ASM Instance. The active site is generally called the production site, and the passive site is called the standby site. Oracle Grid Infrastructure and Oracle RAC make use of Redundant Interconnect Usage that distributes network traffic and ensures optimal communication in the cluster. Additional protection from data center failure with special considerations that are documented in Section 7.1.4.1, Highest level of availability for server or computer room failure. With Oracle Clusterware, you can provide a cold cluster failover to protect an Oracle Database instance from a system or server failure. During the process of resolving conflicts, information may be lost or become corrupted. This architecture is referred to as an extended cluster. The basic function of a cold cluster failover is to monitor a database instance running on a server, and if a failure is detected, to restart the instance on a spare server in the cluster. A logical copy configured and maintained using Oracle GoldenGate is called a replica, not a logical standby database, because it provides many capabilities that are beyond the scope of the normal definition of a standby database. Table 7-3 identifies the additional capabilities provided by the architectures that build on Oracle Database and attempts to label each architecture with its greatest strengths. The observer (thin client watchdog) resides in the application tier and monitors the availability of the primary database. Support for heterogeneous platforms, versions, and character sets. For an Oracle RAC database, each node in a cluster usually has one instance of the running Oracle software that references the database. High availability functionality to manage third-party applications, Rolling release upgrades of Oracle Clusterware. It also allows the storage to be laid out in a different fashion from the primary computer. Fine control of information and data sharing are required. It is based on proven Oracle high availability technologies and recommendations. Oracle Database is a single-instance, standalone (noncluster) database and it is the foundation for all high availability architectures. Oracle RAC - Wikipedia There are numerous high availability features that you can use in the Oracle Database single-instance database architecture. Oracle GoldenGate can capture changes at a source database, and the captured changes can be propagated asynchronously to replica databases. Oracle Database High Availability Best Practices for information about configuring Oracle Database 11g with Oracle RAC on extended clusters, White papers about extended (stretch) clusters and about using standard NFS to support a third voting disk on an extended cluster configuration at http://www.oracle.com/technetwork/database/clustering/overview/. All of the business benefits of Oracle RAC.