Vijay.Cherukuri-Oracle Dec 18 2011 edited Nov 5 2012. In simple terms "Split brain" means that there are 2 or more distinct sets of nodes, or "cohorts", with no communication between the two cohorts. Oracle Flashback Technology optimizes logical failure repair. Oracle Data Guard is designed so that it does not affect the Oracle database writer (DBWR) process that writes to data files, because anything that slows down the DBWR process affects database performance. Configuring symmetric sites is recommended to ensure that each site can accommodate the performance and scalability requirements of the application after any role transition. Oracle Database with Oracle RAC architecture is designed primarily as a scalability and availability solution that resides in a single data center. Maximum RTO for instance or node failure is in seconds. The solutions introduced in this book are described in detail in the Oracle Fusion Middleware High Availability Guide. RAC Split Brain Syndrome. This private network interface or interconnect are redundant and are only used for inter-instance oracle data block transfers. There is no fancy or expensive hardware required. Fast-start failover is recommended to provide automatic failover without user intervention and bounded recovery time. When the instance members in a RAC fail to ping/connect to each other via this private network and continue to process data block independently. You can allocate server resources to multiple instances using Oracle Database Resource Manager Instance Caging. Corruption Prevention, Detection, and Repair detect and prevent some corruptions and lost writes. What Is Oracle RAC. Fast Recovery Area manages local recover-related files automatically. 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/. 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. The production database transmits redo data (either synchronously or asynchronously) to redo log files at the physical standby database. Clusterware will evaluate cluster resources on implied workload 3. . The group(cohort) with more cluster nodes survive But 1 and 2 cannot talk to 3, and vice versa. The center frame shows the configuration during fast-start failover. Online Reorganization and Redefinition allows for dynamic data changes. Provides maximum protection from physical corruptions. 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. Similar to using Oracle Data Guard in SQL Apply mode, Oracle GoldenGate can capture database changes, propagate them to destinations, and apply the changes at these destinations. Oracle RAC Split Brain Syndrome Scenerio oracle-tech If the sub-clusters are of the different sizes, the functionality is same as earlier i.e. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. Choice of RPO equal to zero (SYNC) or near-zero (ASYNC). Oracle recommends that you use the following Oracle features to make a standalone database on a single computer available for certain failures and planned maintenance activities: Fast-Start Fault Recovery bounds and optimizes instance and database recovery times. Oracle Security Features prevent unauthorized access and changes. Table 7-2 recommends architectures based on your business requirements for RTO, RPO, MO, scalability, and other factors. Figure 7-9 Oracle Database with Oracle RAC and Oracle Data Guard - MAA. The figure shows Oracle Database with Oracle Data Guard architecture. FAN with integrated Oracle client failover, including Java applications using UCP with Oracle RAC and Oracle Data Guard. Oracle Grid Infrastructure and Oracle RAC make use of Redundant Interconnect Usage that distributes network traffic and ensures optimal communication in the cluster. It also gives users complete control over the routing of change records from the primary database to a replica database. 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. Footnote2Rolling upgrades with Oracle Data Guard incur minimal downtime. But i want to test it on a test environment in my view for that i need to fail or make the node's to lose connectivity with one another but then continue to . If it takes seconds to detect a malicious DML or DLL transaction, it typically only requires seconds to flash back the appropriate transactions. Maximum RTO for instance or node failure is in minutes. Recovery Manager optimizes local repair of data failures using local backups. When you move the Oracle RAC One Node instance to the newly resized Oracle VM node, you can dynamically increase any limits programmed with Resource Manager Instance Caging. Oracle Automatic Storage Management and Oracle Automatic Storage Management Cluster File System (Oracle ACFS) tolerate storage failures and optimize storage performance and utilization. This is called Split Brain. Provides read-only access to synchronized standby database and fast incremental backups to off-load production. The instances monitor each other by checking "heartbeats." However, an extended cluster cannot protect against all data corruptions or specific data failures that impact the database, or against comprehensive disasters such as earthquakes, hurricanes, and regional floods that affect a greater geographical area. Oracle RAC Interview Questions - Coherence and Split-Brain Database scalability beyond one instance or node. This functionality is available starting with Oracle Database 11g Release 2 (11.2.0.2). Footnote5Storage failures are prevented by using Oracle ASM with mirroring and its automatic rebalance capability. Another possible configuration might be a testing hub consisting of snapshot standby databases. Table 7-2 High Availability Architecture Recommendations. These redundant configurations provide increased availability either through a distributed workload, through a failover setup, or both. Dynamic Resource Provisioning allows for dynamic system changes.