what is split brain in oracle rac what is split brain in oracle rac

There are three typical causes of corruption: Split Brain Condition occurs when a single cluster has a failure that results in reconfiguration of cluster into multiple partitions, with each partition forming its own sub-cluster without the knowledge of the existence of other. Evaluate logical standby databases if additional indexes are required for reporting purposes and if your application only uses data types supported by logical standby database and SQL Apply. For example, for a business that has a corporate campus, the extended Oracle RAC configuration could consist of individual Oracle RAC nodes located in separate buildings. The following list summarizes the advantages of using Oracle Data Guard compared to using remote mirroring solutions: Better network efficiencyWith Oracle Data Guard, only the redo data needs to be sent to the remote site and the redo data can be compressed to provide even greater network efficiency. Q39) Mention what is split brain syndrome in RAC? Figure 7-2 shows a configuration that uses Oracle Clusterware to extend the basic Oracle Database architecture and provide cold cluster failover. host01 is evicted although it has a lower node number. which node first joined the cluster). To protect against site failures, the MAA recommends that Oracle RAC and Oracle Data Guard reside on separate systems (clusters) and data centers. Split Brain Syndrome, In a Oracle RAC environment all the instances/servers communicate with each other using high-speed interconnects on the private network. To simulate loss of connectivity between two nodes, stop the private network service on one of the nodes: Verify that host01 is retained as it has a lower node number and host02 is evicted: To simulate loss of connectivity between two nodes, stop private network service on one of the nodes: Verify that host02 is retained as it has higher number of database services executing and host01 is evicted although it has a lower node number: If the sub-clusters are of the different sizes, the functionality is same as earlier, i.e. In a split brain situation, voting disk is used to determine which node(s) will survive and which node(s) will be evicted. Section 3.4.1 describes how Oracle Clusterware is software that, when installed on servers running the same operating system, enables the servers to be bound together to operate as if they are one server, and manages the availability of user applications and Oracle databases. Run-time performance level management with Oracle Database Quality of Service Management (This functionality is available starting with Oracle Database 11g Release 2 (11.2.0.2)), Zero downtime with Grid Control provisioning, Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patchesFoot1, Database Grid with site failure protection, Simplest high availability, data protection, and disaster-recovery solution, Automatic and fast failover for computer failure, storage failure, data corruption, for configured ORA- errors or conditions and database failures, Rolling upgrade for system, clusterware, database, and operating systemFoot2, Ability to off-load backups to the standby database, Ability to off-load read and reporting workload to the standby database. An infrastructure services provider to the telecommunication industry uses a single standby database located over 400 miles away from the primary database configured for synchronous redo transport, enabling zero-data-loss failover for maximum data protection and high availability. This figure shows Oracle Database with Oracle RAC architecture for a partitioned three-node database. Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. By using specialized devices, this distance can be extended to 66 kilometers. Oracle recommends that you use automatic undo management with sufficient space to attain your desired undo retention guarantee, enable Oracle Flashback Database, and allocate sufficient space and I/O bandwidth in the fast recovery area. This configuration consists of a central resource supporting 10 applications and databases in the grid, rather than managing 10 separate system or storage units in a nongrid infrastructure. Oracle Flashback Technology optimizes logical failure repair. Thus, this feature allows you to consolidate many databases into a single cluster for easier management, while still providing high availability by quickly relocating instances in the event of server failure. Hi Guru's. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). With Oracle Clusterware, . See Section 7.2 for a comparison of the different architectures and highlights of the benefits and considerations. Support for bidirectional replication and updating anything and anywhere. Footnote3Recovery time consists largely of the time it takes to restore the failed system. In the figure, the configuration is operating in normal mode in which Node 1 is the active instance connected to Oracle Database that is servicing applications and users. Start both the services for database admindb so that serv1 executes on host01 and serv2 executes on host02. Oracle Clusterware cold cluster failover combined with Oracle Data Guard makes a tightly integrated solution in which failover to the secondary node in the cold cluster failover is transparent and does not require you to reconfigure the Oracle Data Guard environment or perform additional steps. Start both the services for database admindb so that equal number of database services execute on both the nodes. 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. The sum of benefits of Oracle Clusterware with Oracle Data Guard, Best high availability, data protection, and disaster-recovery solution with scalability built in, The sum of benefits of Oracle RAC with Oracle Data Guard, Oracle Database with Oracle GoldenGateFoot3, Bidirectional replication and information management, Replica database (or databases) available for read/write use, Fast failover for computer failure and storage failure, Minimum downtime for computer or site maintenance and database and application upgrades. The data is derived from actual user experiences and from Oracle service requests. It is possible, under certain circumstances, to build and deploy an Oracle RAC system where the nodes in the cluster are separated by greater distances. There are numerous high availability features that you can use in the Oracle Database single-instance database architecture. In Oracle RAC each node in the cluster is interconnected through a private interconnect. The servers on which you want to run Oracle Clusterware must be running the same operating system. The production database is connected over the network to the physical standby database site and the logical standby database site (the standby databases may be at the same or different sites). For example: Active Data Guard, Redo Apply for physical standby databases, and SQL Apply for logical standby databases, multiple protection modes, push-button automated switchover and failover capabilities, automatic gap detection and resolution, GUI-driven management and monitoring framework, cascaded redo log destinations. This book focuses primarily on the database high availability solutions. The figure shows the same Oracle Data Guard configuration in three different frames, as described in the following list: The leftmost frame shows the configuration before fast-start failover occurs. The following sections provide an overview of Oracle Database high availability architectures and implement the MAA best practices: Oracle Database with Oracle Clusterware (Cold Cluster Failover), Oracle Database with Oracle Real Application Clusters (Oracle RAC), Oracle Database with Oracle Clusterware and Oracle Data Guard, Oracle Database with Oracle RAC One Node and Oracle Data Guard, Oracle Database with Oracle RAC and Oracle Data Guard. Building on top of the local high availability solutions is the Oracle Application Server disaster recovery solution. Figure 7-1 shows a basic, single-node Oracle Database that includes an Oracle ASM instance.Foot1 This architecture incorporates several high availability features, including Flashback Database, Online Redefinition, Recovery Manager, and Oracle Secure Backup. Oracle Enterprise Manager support for patch application simplifies software maintenance. 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. Oracle Data Guard transmits redo data from the primary database to the secondary site to keep the databases synchronized. Figure 7-7 shows the production database at the primary site and multiple standby databases at secondary sites. Oracle Clusterware provides a number of benefits over third-party clusterware. If the fast recovery area is on the source volume that is remotely mirrored, then you must also remotely mirror the flashback logs. But 1 and 2 cannot talk to 3, and vice versa. If the primary database uses the asynchronous redo transport, configure your maximum data loss tolerance or the Oracle Data Guard broker's FastStartFailoverLagLimit property to meet your business requirements. The logical standby database may contain additional indexes and materialized views. During the process of resolving conflicts, information may be lost or become corrupted. High availability benefits and workload balancing outweigh performance concerns. At a high level, Oracle Application Server local high availability architectures include several active-active and active-passive architectures for the OracleAS middle-tier and the OracleAS Infrastructure. Split Brain Syndrome in RAC. Figure 7-9 shows the recommended MAA configuration, with Oracle Database, Oracle RAC, and Oracle Data Guard. They will enhance your knowledge and help you to emerge as the best candidate. Oracle Grid Infrastructure and Oracle RAC make use of Redundant Interconnect Usage that distributes network traffic and ensures optimal communication in the cluster. Customer can designate which server(s) and resource(s) are critical 2. Footnote2Oracle ASM automatically rebalances stored data when disks are added or removed while the database remains online. Network addresses are failed over to the backup node. If zero data loss is required with minimum performance impact on the primary database, then the best practice is to locate the secondary site within 200 miles of the primary database. The SELECT statement is used to retrieve information from a database. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). For availability reasons, the Oracle database is a single database that is mirrored at both of the sites. For data resident in Oracle databases, Oracle Data Guard, with its built-in zero-data-loss capability, is more efficient, less expensive, and better optimized for data protection and disaster recovery than traditional remote mirroring solutions. See Section 1.5, "Roadmap to Implementing the Maximum Availability Architecture (MAA)" for more information about the best practices documentation. The individual nodes are running fine and can accept user connections and work . This is because corruptions introduced on the production database probably can be mirrored by remote mirroring solutions to the standby site, but corruptions are eliminated by Oracle Data Guard. With Oracle Clusterware, you can provide a cold cluster failover to protect an Oracle Database instance from a system or server failure. Oracle Data Guard is operating in a steady state, with the primary database transmitting redo data to the target standby database and the observer monitoring the state of the entire configuration. 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. Then this process is referred as Split Brain Syndrome. Figure 7-7 Oracle Database with Oracle Data Guard on Primary and Multiple Standby Sites, Oracle Data Guard Concepts and Administration for more information about the various types of standby databases and to find out what data types are supported by logical standby databases, Oracle Database High Availability Best Practices for configuration best practices, The "Managing Data Guard Configurations Having Multiple Standby Databases - Best Practices" white paper, and other Oracle Data Guard white papers at. These solutions are categorized into local high availability solutions that provide high availability in a single data center deployment, and disaster-recovery solutions, which are usually geographically distributed deployments that protect your applications from disasters such as floods or regional network outages. Table 7-5 Attainable Recovery Times for Planned Outages, System change - Dynamic Resource Provisioning. The term "Split-Brain" is often used to describe the scenario when two or more co-operating processes in a distributed system, typically a high availability cluster, lose connectivity with one another but then continue to operate independently of each other, including acquiring logical or physical resources, under the incorrect assumption . Their strategy further mitigates risk by maintaining multiple standby databases, each implemented using a different architecturesRedo Apply and SQL Apply. These devices convert ESCON or Fibre Channel to the appropriate IP, ATM, or SONET networks. Oracle Data Guard provides a compelling set of technical and business reasons that justify its adoption as the disaster recovery and data protection technology of choice, over traditional remote mirroring solutions. Oracle RAC Split Brain Syndrome Scenerio. Provides seamless integration with, and migration to, Oracle Real Application Clusters (Oracle RAC) and Oracle Data Guard. Voting disk is used by Oracle Cluster Synchronization Services Daemon (ocssd) on each node, to mark its own attendance and also to record the nodes it can communicate with. 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. Oblivious of the existence of other cluster fragments, each sub-cluster continues to operate independently of the others. the clusterware identifies the largest sub-cluster, and aborts all the nodes which do. In addition, allowing maintenance operations to occur on a subset of components in the cluster while the application continues to run on the rest of the cluster can reduce planned 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 operate independently of each other. The Oracle Data Guard broker communicates with the production database, the physical standby database, and the logical standby database. Oracle Data Guard provides a number of advantages over traditional solutions, including the following: Fast, automatic or automated database failover for data corruptions, lost writes, and database and site failures, Automatic corruption repair automatically replaces a corrupted block on the primary or physical standby by copying a good block from a physical standby or primary database, Most comprehensive protection against data corruptions and lost writes on the primary database, Reduced downtime for storage, Oracle ASM, Oracle RAC, system migrations and some platform migrations, and changes using Data Guard switchover, Reduced downtime with Oracle Data Guard rolling upgrade capabilities, Ability to off-load primary database activitiessuch as backups, queries, or reportingwithout sacrificing the RTO and RPO ability to use the standby database as a read-only resource using the real-time query apply lag capability, Ability to integrate non-database files using Oracle Database File System (DBFS) as part of the full site failover operations, No need for instance restart, storage remastering, or application reconnections after site failures, Transparent and integrated support for application failover. What Is Oracle RAC. The Maximum Availability Architecture (MAA) is Oracle's best practices blueprint. 1. 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. However, remote mirroring solutions affect DBWR process performance because they subject all DBWR process write I/O's to network and disk I/O induced delays inherent to synchronous, zero-data-loss configurations. This private network interface or interconnect are redundant and are only used for inter-instance oracle data block transfers. Furthermore, operational practices across role transitions are simplified when the sites are symmetric. A global manufacturing company used Oracle Data Guard to replace storage-based remote mirroring and maintain a standby database at its recovery site 50 miles away from the primary site. Also, see Figure 5-2 for another example of a multiple standby database environment. It allows you to select the table columns depending on a set of criteria. To provide this transparent failover capability, Oracle Clusterware requires a virtual IP (VIP) address for each node in the cluster. As per Split brain syndrome in Oracle RAC in case of inter-connect failures the master node will evict other/dead nodes . In Oracle RAC, all the instances/servers communicate with each other using a private network. Logical or user failures that manipulate logical data (DMLs and DDLs).