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. which node first joined the cluster). Prior to Oracle Database 12.1.0.2c, the algorithm to determine the node(s) to be retained / evicted is as follows: However, starting from 12.1.0.2c, in case of split brain, some improvement has been made to node eviction algorithm. 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/. The following list describes examples of Oracle Data Guard configurations using multiple standby databases: A world-recognized financial institution uses two remote physical standby databases for continuous data protection after failover. In Oracle RAC, all the instances/servers communicate with each other using a private network. 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. See Section 1.5, "Roadmap to Implementing the Maximum Availability Architecture (MAA)" for more information about the best practices documentation. The fast-start failover has completed and the target standby database is running in the primary database role. Site configurations are on heterogeneous platforms. Maximum RTO for instance or node failure is in seconds to minutes. 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. 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. Maximum RTO for instance or node failure is in minutes. End-users connect to clusters through a public network. Applications can easily mask failures to the end user. the. Fast Recovery Area manages local recover-related files automatically. All of the business benefits of Oracle RAC. (adsbygoogle=window.adsbygoogle||[]).push({}); 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 using the said resources. The public and private interconnects, and the Storage Area Network (SAN) are all on separate dedicated channels, with each one configured redundantly. 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. When a database is started, Oracle Database allocates a memory area called the System Global Area (SGA) and starts one or more Oracle Database processes. There is no fancy or expensive hardware required. Split Brain Syndrome Basic Concept in Oracle RAC. 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. 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. If the observer is unable to regain a connection to the primary database within the specified time, and the target standby database is ready for fast-start failover, then fast-start failover ensues. The following list describes some implementations for a multiple standby database architecture: Continuous and transparent disaster or high availability protection if an outage occurs at the primary database or the targeted standby database, Regional reporting or reader databases for better response time, Synchronous redo transport that transmits to a more local standby database, and asynchronous redo transport that transmits to a more remote standby database for optimum levels of performance and data protection, Transient logical standby databases (described in Section 3.6.3) for minimal downtime rolling upgrades, Test and development clones using snapshot standby databases (described in Section 3.6.4), Scaling the configuration by creating additional logical standby databases or snapshot standby databases. Oracle Database with Oracle GoldenGate provides granularity and control over what is replicated and how it is replicated. Thus, compared to Oracle Data Guard, a remote mirroring solution must transmit each change many more times to the remote site. In Oracle RAC, all the instances/servers communicate with each other using a private network. A telecommunications provider uses asynchronous redo transport to synchronize a primary database on the West Cost of the United States, with a standby database on the East Coast, over 3,000 miles away. These updates are discarded when the snapshot database is reconverted to a physical standby database. The premise of the Data Guard hub is that it provides higher utilization with lower cost. 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. With the Oracle Grid technologies, you can enable a high level of usage and low TCO without sacrificing business requirements. From the entry point to an Oracle Application Server system (content cache) to the back-end layer (data sources), all the tiers that are crossed by a request can be configured in a redundant manner with Oracle Application Server. The application VIP is tied to the application by making it dependent on the application resource defined by Cluster Ready Services (CRS). Oracle Database with Oracle RAC on Extended Clusters. The Oracle Data Guard broker communicates with the production database, the physical standby database, and the logical standby database. By using specialized devices, this distance can be extended to 66 kilometers. 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. 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. 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. 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. Provides seamless integration with, and migration to, Oracle Real Application Clusters (Oracle RAC) and Oracle Data Guard. Oracle Application Server instances can be installed in either site as long as they do not interfere with the instances in the disaster recovery setup. Although cold cluster failover is not shown in Figure 7-8, you can configure it by adding a passive node on the secondary site. Oracle Clusterware provides a number of benefits over third-party clusterware. 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. Automatic block repair may be possible, thus eliminating any downtime in an Oracle Data Guard configuration. To ensure data consistency, each instance of a RAC database needs to keep heartbeat with the other instances. Oracle Clusterware: Enables you to use an entire software solution from Oracle, avoiding the cost and complexity of maintaining additional cluster software. A highly available and resilient application requires that every component of the application must tolerate failures and changes. For example : In a split brain situation, voting disk is used to determine which node(s) will survive and which node(s) will be evicted. 12) Mention what is split brain syndrome in RAC? A single standby database architecture consists of the following key traits and recommendations: Standby database resides in Site B. 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. Typically, this is not possible with remote mirroring solutions. The problem which could arise out of this situation is that the sane . 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. 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. The probability of failing over all databases at the same time is unlikely. These figures show how you can use the Oracle Clusterware framework to make both Oracle Database and your custom applications highly available. Uses a private network and voting disk-based communication to detect and resolve split-brainFoot2 scenarios. Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patches. Data Recovery Advisor diagnoses persistent (on disk) data failures, presents appropriate repair options, and runs repair operations at your request. 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. The operation of an Oracle Clusterware cold cluster failover is depicted in Figure 7-2 and Figure 7-3. In Oracle RAC each node in the cluster is interconnected through a private interconnect. It allows you to select the table columns depending on a set of criteria. 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.