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Recovery Manager (RMAN) optimizes local repair of data failures. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. It is based on proven Oracle high availability technologies and recommendations. Limited support for mixed platforms. 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. Oracle Database with Oracle RAC architecture is designed primarily as a scalability and availability solution that resides in a single data center. 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 ). Oracle Clusterware provides tolerance of node failures, whereas Oracle Data Guard provides additional protection against data corruptions, lost writes, and database and site failures. For example : However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. 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. Footnote6Recovery time for human errors depend primarily on detection time. With Oracle RAC integration, database scalability is possible. Whatever the case, these Oracle RAC interview questions and answers are for you. To provide this transparent failover capability, Oracle Clusterware requires a virtual IP (VIP) address for each node in the cluster. Split Brain is often used to describe the scenario when two or more nodes in a 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 that the other process (es) are no longer operational or . 1. Willing to make additional provisions for remote data protection to protect against database, data, and cluster failures and corruptions. Where two or more instances . Figure 7-7 shows the production database at the primary site and multiple standby databases at secondary sites. The figure shows Oracle Database with Oracle Data Guard architecture. The instances monitor each other by checking "heartbeats." All single-instance high availability features, such as the Flashback technologies and online reorganization, also apply to Oracle RAC. Table 7-5 compares the attainable recovery times of each Oracle high availability architecture for all types of planned downtime. 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. All of the business benefits of Oracle RAC and Oracle Data Guard. Oracle Restart enhances the availability of Oracle databases, listeners, and Oracle ASM instances in a single-instance environment by monitoring and automatically restarting Oracle processes. These devices convert ESCON or Fibre Channel to the appropriate IP, ATM, or SONET networks. This architecture is identical to the single-standby database architecture that was described in Section 7.1.5.1, except that there are multiple standby databases in the same Oracle Data Guard configuration. You should determine if both sites are likely to be affected by the same disaster. Support for fine-grained, n-way multimaster, hub-and-spoke, or many-to-one replication architectures. We will verify that when an equal number of database services are running on both nodes, the node with lower node number (host01) survives. 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. The problem which could arise out of this situation is that the sane . 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. The split brain syndrome and its affects and how it has been managed in oracle is mentioned below. 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. Configuring symmetric sites is recommended to ensure that each site can accommodate the performance and scalability requirements of the application after any role transition. The probability of failing over all databases at the same time is unlikely. Customer can designate which server(s) and resource(s) are critical 2. Name of the cluster: Cluster01.example.com, Number of nodes: 3 (host01, host02, host03), Instances of RAC database: admindb1 on host01. host02 is retained as it has higher number of database services executing. The individual nodes are running fine and can accept user connections and work . the number of database services executing on a node. Following the execution of a SELECT statement, a tabular result is held in a result table (called a result set). mysql - Split brain scenario - RAC and PXC - Database Administrators Provides maximum protection from physical corruptions. Network connection changes and other site-specific failover activities may lengthen overall recovery time. The new primary database starts transmitting redo data to the new standby database. Table 7-5 Attainable Recovery Times for Planned Outages, System change - Dynamic Resource Provisioning. The rightmost frame shows the configuration after fast-start failover has occurred. 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. 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. The group(cohort) with lower node member survive, in case of same number of node(s) available in each group. With the snapshot standby database hub, you can use the combined storage and server resources of a grid instead of building and managing individual servers for each application. Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patches. There are numerous high availability features that you can use in the Oracle Database single-instance database architecture. If the primary system should fail, the first standby database becomes the new primary database. Now talking about split-brain concept with respect to oracle . Oracle Application Server provides redundancy by offering support for multiple instances supporting the same workload. 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. Includes all of the features required for cluster management, including node membership, group services, global resource management, and high availability functions such as managing third-party applications, event management, and Oracle notification services that enable Oracle clients to reconnect to the new primary database after a failure. The servers on which you want to run Oracle Clusterware must be running the same operating system. Server scalability is unlimited, and if applications grow to require more resources than a single node can supply, you can perform an online upgrade to a traditional multinode Oracle RAC configuration. The active site is generally called the production site, and the passive site is called the standby site. 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. Please enroll for the Oracle DBA Interview Question Course.https://learnomate.org/courses/oracle-dba-interview-question/Use DBA50 to get 50% discountPlease s. What is Voting Disk & Split Brain Syndrome in RAC 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. Online Patching allows for dynamic database patches for diagnostic and interim patches. Online Reorganization and Redefinition allows for dynamic data changes. Oracle RAC Interview Questions - Coherence and Split-Brain This would lead to collision and corruption of shared data as each sub-cluster assumes ownership of shared data. Footnote5Storage failures are prevented by using Oracle ASM with mirroring and its automatic rebalance capability. 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 . Communication among the nodes is optimized by means of Redundant Interconnect Usage (without requiring the use of bonding or other technologies) to provide stability, reliability, and scalability. 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. Oracle RAC Split Brain Syndrome Scenerio. 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. After the former primary database has been repaired, the observer reestablishes its connection to that database and reinstates it as a new standby database. Fast-start failover is recommended to provide automatic failover without user intervention and bounded recovery time. For more information, see the "Administering Oracle RAC One Node" section in the Oracle Real Application Clusters Administration and Deployment Guide. Oracle Data Guard is a high availability and disaster-recovery solution that provides very fast automatic failover (referred to as fast-start failover) in database failures, node failures, corruption, and media failures. Prior to Oracle Database 12.1.0.2c, the algorithm to determine the node (s) to be retained / evicted is as follows: If the sub-clusters are of the different sizes, the clusterware identifies the largest sub-cluster . Providing application-specific failure detection means Oracle Clusterware can fail over not only during the obvious cases such as when the instance is down, but also in the cases when, for example, an application query is not meeting a particular service level. Furthermore, the standby databases can be used for read-only access and subsequently for reader farms, for reporting, and for testing and development. 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. Then there are two cohorts: {1, 2} and {3}. Section 7.1.8 describes how you can achieve the highest level of availability with Oracle RAC and Oracle Data Guard. In a "split brain" situation, voting disk is used to determine which node (s) will survive and which node (s) will be evicted. But 1 and 2 cannot talk to 3, and vice versa. Oracle Clusterware manages the availability of both the user applications and Oracle databases. To avoid splitbrain, node 2 aborted itself. Oracle Data Guard is designed to allow businesses get something useful out of their expensive investment in a disaster-recovery site. Split Brain Condition - STOMITH STONITH fencing - dba-oracle.com Footnote2Oracle ASM automatically rebalances stored data when disks are added or removed while the database remains online. They will enhance your knowledge and help you to emerge as the best candidate. These best practices are required to maximize the benefits of each architecture. The fast-start failover has completed and the target standby database is running in the primary database role. 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. In Oracle RAC, all the instances/servers communicate with each other using a private network. 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. The premise of the Data Guard hub is that it provides higher utilization with lower cost. However, when the data centers are located more than 66 kilometers apart, you must use a series of repeaters and converters from third-party vendors. The script content on this page is for navigation purposes only and does not alter the content in any way. Common messages in instance alert log are similar to: In above example, instance 2 LMD0 (pid 29940) is the receiver in IPC Send timeout. 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 center frame shows the configuration during fast-start failover. By using specialized devices, this distance can be extended to 66 kilometers. Oracle RAC One Node allows you to run one instance of an Oracle RAC database on a single node in a cluster. Node 1 is connected to Node 2 and to the Oracle database, but Node 1 is currently idle, in standby mode. The configuration can be an active-active configuration using Oracle Application Server Cluster or an active-passive configuration using Oracle Application Server Cold Cluster Failover.