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Split brain syndrome occurs when the instances in a RAC fails to connect or ping to each other via the private interconnect, Although the servers are physically up and running and the database instances on these servers is also running. 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 the MAA white paper "Rapid Oracle RAC One Node Standby Deployment" at. If all the sub-clusters are of the same size, the sub-cluster having the lowest numbered node survives so that, in a 2-node cluster, the node with the lowest node number will survive. Please enroll for the Oracle DBA Interview Question Course.https://learnomate.org/courses/oracle-dba-interview-question/Use DBA50 to get 50% discountPlease s. Provides read-only access to synchronized standby database and fast incremental backups to off-load production. Ina cluster, a private interconnect is used by cluster nodes to monitor each nodes status and communicate with each other. The Maximum Availability Architecture (MAA) is Oracle's best practices blueprint. High availability functionality to manage third-party applications, Rolling release upgrades of Oracle Clusterware. Node Weighting for Split Brain Resolution Without better understanding of what is critical or of higher priority to the customer's workload, Oracle Clusterware has always resolved split brain conditions in favor of the cluster cohort containing the node with the lowest node number (i.e. In Oracle Database 11g Release 2 (11.2), Oracle RAC One Node or Oracle RAC is the preferred solution over Oracle Clusterware (Cold Cluster Failover) because it is a more complete and feature-rich solution. Outages or data loss that could affect customer service and safety are avoided by using Oracle Data Guard synchronous transport and automatic failover (fast-start failover). For an Oracle RAC database, each node in a cluster usually has one instance of the running Oracle software that references the database. Footnote8With automatic block repair, this should be the most common block corruption repair. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). If it takes seconds to detect a malicious DML or DLL transaction, it typically only requires seconds to flash back the appropriate transactions. Typically, this is not possible with remote mirroring solutions. Oracle Grid Infrastructure and Oracle RAC make use of Redundant Interconnect Usage that distributes network traffic and ensures optimal communication in the cluster. 1. the clusterware identifies the largest sub-cluster, and aborts all the nodes which do NOT belong to that sub-cluster. For physical standby databases, this solution: Supports very high primary database throughput. Figure 7-5 shows an Oracle RAC extended cluster for a configuration that has multiple active instances on six nodes at two different locations: three nodes at Site A and three at Site B. In order to make largest number of resources available to the users, the node weight is computed for each node based on number of the resource executing on it and the sub-cluster with higher weight will survive.