what is split brain in oracle rac

The Oracle Data Guard broker communicates with the production database, the physical standby database, and the logical standby database. Figure 7-9 shows the recommended MAA configuration, with Oracle Database, Oracle RAC, and Oracle Data Guard. 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 . Oracle Enterprise Manager support for patch application simplifies software maintenance. With either the active-active or the active-passive category, multiple solutions exist that differ in ease of installation, cost, scalability, and security. Maximum RTO for instance or node failure is in seconds to minutes. Footnote3Recovery time consists largely of the time it takes to restore the failed system. Unlike a traditional monolithic database server that is expensive and is not flexible to changing capacity and resource demands, Oracle RAC combines the processing power of multiple interconnected computers to provide system redundancy, scalability, and high availability. For example, if a stray write occurs to a disk, or there is a corruption in the file system, or the host bus adaptor corrupts a block as it is written to disk, then a remote mirroring solution may propagate this corruption to the disaster-recovery site. Even though split brain scenario occurs in both Oracle RAC and Percona's XtraDB Cluster, a two node cluster is allowed and split brain scenario is resolved in RAC but a two node is not recommended in Percona Cluster ( 3 nodes is recommended ). A global provider of information services to legal and financial institutions uses multiple standby databases in the same Oracle Data Guard configuration to minimize downtime during major database upgrades and platform migrations. The SELECT statement is used to retrieve information from a database. Furthermore, operational practices across role transitions are simplified when the sites are symmetric. Split Brain Syndrome | Oracle Database Internal Mechanism Clients on the network experience a period of lockout while the failover occurs and are then served by the other database instance after the instance has started. Recovery Manager (RMAN) optimizes local repair of data failures. 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. 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. Oracle Flashback Technology optimizes logical failure repair. Glossary - Oracle The production database transmits redo data (either synchronously or asynchronously) to redo log files at the physical standby database. Hence, we observed that when an equal number of database services were running on both nodes, the node with lower node number (host01) survives. Also, you can use the Oracle Clusterware ability to relocate applications and application resources (using the crsctl relocate resource command) as a way to move the workload to another node so that you can perform planned system maintenance on the production server. Although cold cluster failover is not shown in Figure 7-8, you can configure it by adding a passive node on the secondary site. If the primary system should fail, the first standby database becomes the new primary database. Online Application Maintenance and Upgrades with Edition-based redefinition allows an application's database objects to be changed without interrupting the application's availability. Consider using Oracle Database with Oracle GoldenGate if one or more of the following conditions are true: Updates are required on both sites or databases, and the changes must be propagated bidirectionally. Compared to mirroring, Oracle Data Guard provides better performance and is more efficient, Oracle Data Guard always verifies the state of the standby database and validates the data before applying redo data, and Oracle Data Guard enables you to use the standby database for updates while it protects the primary database. This chapter describes the various high availability architectures in an Oracle environment and helps you to choose the correct architecture for your organization. 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. Any of these processes experience IPC Send time out will incur communication reconfiguration and instance eviction to avoid split brain. If the sub-clusters are of the different sizes, the functionality is same as earlier i.e. There are some corruptions that cannot be addressed by automatic block repair, and for those we can rely on Data Guard failover that takes seconds to minutes. Online Reorganization and Redefinition allows for dynamic data changes. the number of database services executing on a node. Another possible configuration might be a testing hub consisting of snapshot standby databases. Both the primary and secondary sites contain Oracle Application Servers, two database instances, and an Oracle database. The Oracle Application Server High Availability Guide describes the following high availability services in Oracle Application Server in detail: Process death detection and automatic restart. If all the sub-clusters are of the same size, the functionality has been modified as: If the sub-clusters have equal node weights, the sub-cluster with the lowest numbered node in it survives so that, in a 2-node cluster, the node with the lowest node number will survive. Split Brain: What's new in Oracle Database 12.1.0.2c? 1. Node 2 is connected to Node 1 and to Oracle Database, but it is currently standby mode. Higher ROIBusinesses must obtain maximum value from their IT investments, and ensure that no IT infrastructure is sitting idle. FAN with integrated Oracle client failover, including Java applications using UCP with Oracle RAC and Oracle Data Guard. Online Patching allows for dynamic database patches for diagnostic and interim patches. By using specialized devices, this distance can be extended to 66 kilometers. For high availability, Oracle recommends that you have a minimum of three voting disks. All single-instance high availability features, such as the Flashback technologies and online reorganization, also apply to Oracle RAC. Start both the services for database admindb so that serv1 executes on host01 and serv2 executes on host02. Table 7-5 compares the attainable recovery times of each Oracle high availability architecture for all types of planned downtime. 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). Split brain syndrome in RAC - Oracle Forums This unique solution combines the proven Oracle Data Guard technology in Oracle Database with advanced disaster recovery technologies in the application realm to create a comprehensive disaster recovery solution for the entire application system. Let say 2 node RAC configuration node 1 is defined as master node (by some parameter like load and others) incase of network failures node 1 will terminate node 2 . Oracle Net Services provide client access to the Application/Web server tier at the top of the figure, Figure 7-4 Oracle Database with Oracle RAC Architecture. With Oracle Clusterware, you also define an application VIP so that users can access the application independently of the node in the cluster where the application is running. Rolling upgrade for system, clusterware, database, and operating system. Rolling upgrade and patch capabilities for Oracle Clusterware with zero database downtime. For logical standby databases, this solution: Provides the simplest form of one-way logical replication, Allows for structural changes to the standby database, such as changes to local tables, adding schemas, indexes, and materialized views, Off-loads production by providing read-only access to a synchronized standby database and allows read/write access to local tables that are not being modified by the primary database, All of the business benefits of Oracle Clusterware (cold cluster failover) and Oracle Data Guard. We will verify that when an unequal number of database services are running on the two nodes, the node hosting the higher number of database services survives even if it has a higher node number. This private network interface or interconnect are redundant and are only used for inter-instance oracle data block transfers. 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. Willing to make additional provisions for remote data protection to protect against database, data, and cluster failures and corruptions. See Section 1.5, "Roadmap to Implementing the Maximum Availability Architecture (MAA)" for more information about the best practices documentation. The recommended high availability and disaster-recovery architectures that use Oracle Data Guard are described in the following sections: Overview of Single Standby Database Architectures, Overview of Multiple Standby Database Architectures. Oracle Data Guard Advantages Compared to Remote Mirroring Solutions. Many high availability architectures today use clusters alone to provide some rudimentary node redundancy and automatic node failover. Footnote1Architectures for which the MO is high might require additional time and expertise to build and maintain, but offer increased flexibility and capabilities required to meet specific business requirements. Name of the cluster: Cluster01.example.com, Number of nodes: 3 (host01, host02, host03), Instances of RAC database: admindb1 on host01. Figure 7-8 shows an Oracle Clusterware and Oracle Data Guard architecture that consists of a primary and a secondary site. c. Some improvement has been made to ensure node(s) with lower load survive in case the eviction is caused by high system load. Disaster strikes the primary database, and its network connections to both the observer and the target standby database are lost. Oracle RAC Interview Questions - Coherence and Split-Brain For physical standby databases, this solution: Supports very high primary database throughput. 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. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. These updates are discarded when the snapshot database is reconverted to a physical standby database. These figures show how you can use the Oracle Clusterware framework to make both Oracle Database and your custom applications highly available. Oracle Automatic Storage Management (Oracle ASM) and Oracle Automatic Storage Management Cluster File System (Oracle ACFS) tolerate storage failures and optimize storage performance and usage. It also gives users complete control over the routing of change records from the primary database to a replica database. Footnote5Storage failures are prevented by using Oracle ASM with mirroring and its automatic rebalance capability. 2. The observer (thin client watchdog) resides in the application tier and monitors the availability of the primary database. Suppose there are 3 nodes in the following situation. So, in a two node situation both the instances will think that the other instance is down because of lack of connection. Also, for large data centers with a need to support many applications with Oracle Data Guard requirements, you can build an Oracle Data Guard hub to reduce the total cost of ownership. Starting from 12.1.0.2, during split brain resolution, the new algorithm followed to decide the nodes to be evicted/retained is as follows: Fortnightly newsletters help sharpen your skills and keep you ahead, with articles, ebooks and opinion to keep you informed. You can define multiple application VIPs, with generally one application VIP defined for each application running. 12) Mention what is split brain syndrome in RAC? The script content on this page is for navigation purposes only and does not alter the content in any way. We will verify that when an equal number of database services are running on both nodes, the node with lower node number (host01) survives. Suppose there are 3 nodes in the following situation. With Oracle RAC integration, database scalability is possible. Maximum RTO for instance or node failure is zero for the databaseFootref1. However, when you use Oracle Clusterware, there is no need or advantage to using third-party clusterware. 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. What is split brain in Oracle RAC? - pehdk.afphila.com Oracle RAC Split Brain Syndrome Scenerio oracle-tech You might choose to use Oracle GoldenGate to configure and maintain a logical copy of your production database. This scenario enables the provider to use existing data centers that are geographically isolated, offering a unique level of high availability. Flexible propagation and management of data, transactions, and events. What is Voting Disk & Split Brain Syndrome in RAC Node 1 is connected to Node 2 and to the Oracle database, but Node 1 is currently idle, in standby mode. In such a scenario, integrity of the cluster and its data might be compromised due to uncoordinated writes to shared data by independently operating nodes. The data is derived from actual user experiences and from Oracle service requests. Then there are two cohorts: {1, 2} and {3}. Now talking about split-brain concept with respect to oracle . Figure 7-1 Single-Node, Nonclustered Oracle Database with an Oracle ASM Instance. The servers on which you want to run Oracle Clusterware must be running the same operating system. 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. The high availability benefits to using Oracle RAC One Node include the following: Offers better database availability than traditional cold failover solutions, Provides better virtualization for databases than hypervisor-based solutions, Enables online migration of database instances and online patching and upgrading of operating system and database software (incurring no downtime), Delivers a comprehensive, single-vendor solution, with no need to implement third-party products, Is ready to scale and upgrade to multinode Oracle RAC, Provides a standardized environment and a common toolset for both single-node and multinode Oracle database deployments, Is less expensive than cold fail over solutions or a full Oracle RAC deployment. Typically, this is not possible with remote mirroring solutions. Maximum RTO for data corruptions, database, or site failures is in seconds to minutes. The fast-start failover has completed and the target standby database is running in the primary database role. Figure 7-6 Primary and Standby Databases and the Observer During Fast-Start Failover. 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. 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/. When a node is physically up and running and database instances are also running fine, but private interconnect fails between two or more nodes and an . Then this process is referred as Split Brain Syndrome. Oracle Application Server provides high availability and disaster recovery solutions for maximum protection against any kind of failure with flexible installation, deployment, and security options. Better performanceOracle Data Guard only transmits write I/Os to the redo log files of the primary database, whereas remote mirroring solutions must transmit these writes and every write I/O to data files, additional members of online log file groups, archived redo log files, and control files. The split brain syndrome and its affects and how it has been managed in oracle is mentioned below. For availability reasons, the Oracle database is a single database that is mirrored at both of the sites. Oracle Grid Infrastructure and Oracle RAC make use of Redundant Interconnect Usage that distributes network traffic and ensures optimal communication in the cluster. 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. Applications scale in an Oracle RAC environment to meet increasing data processing demands without changing the application code. When a node is physically up and running and database instances are also running fine, but private interconnect fails between two or more nodes and an instance member fails to connect or ping to one . Clients are connected to the logical standby database and can work with its data. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. 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. Check that only two nodes (host01 and host02) are active and host01 has lower node number: Create two singleton services for the RAC database admindb: Verify that admindb is the only database in the cluster having its instances executing on host01 and host02. For an Oracle RAC database, each node in a cluster usually has one instance of the running Oracle software that references the database. In previous releases, technologies like bonding or trunking were used to make use of redundant networks for the interconnect. A highly available application must analyze every component that affects the application, including the network topology, application server, application flow and design, systems, and the database configuration and architecture. Whatever the case, these Oracle RAC interview questions and answers are for you. Limited support for mixed platforms. The clusters that are typical of Oracle RAC environments can provide continuous service for both planned and unplanned outages. All of the business benefits of Oracle RAC and Oracle Data Guard. Split Brain in RAC Database | RAC DBA Training - YouTube Common messages in instance alert log are similar to: In above example, instance 2 LMD0 (pid 29940) is the receiver in IPC Send timeout. Online Patching allows for dynamic database patching of typical diagnostic patches. Upon detecting the break in communication, the observer attempts to reestablish a connection with the primary database for the amount of time defined by the FastStartFailoverThreshold property before initiating a fast-start failover. 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.

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