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. In the figure, Node 2 is now the active instance connected to the Oracle database and servicing applications and users. By reducing the combinations of software that you must coordinate and support, you can increase the manageability and availability of your system software. At the snapshot standby database redo data is received, but it is not applied until the snapshot standby database is reconverted to a physical standby database. 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. These figures show how you can use the Oracle Clusterware framework to make both Oracle Database and your custom applications highly available. Oracle Application Server provides redundancy by offering support for multiple instances supporting the same workload. 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 ). I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). For virtualization, Oracle RAC One Node with Oracle VM increases the benefit of Oracle VM with the high availability and scalability of Oracle RAC. For example, you can put the files on different disks, volumes, file systems, and so on. 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. 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. (adsbygoogle=window.adsbygoogle||[]).push({}); The biggest risk following a Split-Brain event is the potential for corrupting system state. The figure shows users making local updates to the snapshot standby database. 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. 1. Footnote8With automatic block repair, this should be the most common block corruption repair. 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. Oracle Security Features prevent unauthorized access and changes. Q39) Mention what is split brain syndrome in RAC? Figure 7-3 shows the Oracle Clusterware configuration after a cold cluster failover has occurred. 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. 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. Clusterware will evaluate cluster resources on implied workload 3. . The advantages to using Oracle RAC on extended clusters include: Ability to fully use all system resources without jeopardizing the overall failover times for instance and node failures, Extremely rapid recovery if one site fails, All of the Oracle RAC benefits listed in Section 7.1.4. The group(cohort) with more cluster nodes survive For more information, see Oracle Data Guard Concepts and Administration or the Oracle Streams Replication Administrator's Guide. 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 clusters that are typical of Oracle RAC environments can provide continuous service for both planned and unplanned outages. For more information, see "Data Guard Support for Heterogeneous Primary and Physical Standbys in Same Data Guard Configuration" in My Oracle Support Note at, https://support.oracle.com/CSP/main/article?cmd=show&type=NOT&id=413484.1. These devices convert ESCON or Fibre Channel to the appropriate IP, ATM, or SONET networks. The common voting result will be: a. 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. Online Patching allows for dynamic database patches for diagnostic and interim patches. Section 7.1.8 describes how you can achieve the highest level of availability with Oracle RAC and Oracle Data Guard. Figure 7-9 shows the recommended MAA configuration, with Oracle Database, Oracle RAC, and Oracle Data Guard. Table 7-3 Additional Capabilities of High Level Oracle High Availability Architectures, The foundation for all high availability architectures. Although using Oracle GoldenGate might require additional work, it offers increased flexibility that might be necessary to meet specific business requirements. Provides seamless integration with, and migration to, Oracle Real Application Clusters (Oracle RAC) and Oracle Data Guard. See Oracle Data Guard Broker for a detailed description of the observer. A nationally recognized insurance provider in the U.S. maintains two standby databases in the same Oracle Data Guard configuration: one physical standby and one logical standby database. Thus, we observed that when unequal number of database services are running on the two nodes, the node with higher number of database services survives even though it has a higher node number. Hi Guru's. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). 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. This architecture is the recommended configuration for Maximum Availability Architecture (MAA). In a split brain situation, voting disk will be used to determine which node(s) survive and which node(s) will be evicted. 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. 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. Footnote2Rolling upgrades with Oracle Data Guard incur minimal downtime. Fast-Start Fault Recovery bounds and optimizes instance and database recovery times to minutes. Maximum RTO for instance or node failure is in minutes. To avoid splitbrain, node 2 aborted itself. See Section 7.1.3, "Oracle Database with Oracle RAC One Node" for more information. Traditionally, Oracle RAC is used in a multinode architecture, with many separate database instances running on separate servers. (For complete disaster recovery and data protection, use the architecture shown in Figure 7-8.). If it takes seconds to detect a malicious DML or DLL transaction, it typically only requires seconds to flash back the appropriate transactions. This private network interface or interconnect are redundant and are only used for inter-instance oracle data block transfers. 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. Network connection changes and other site-specific failover activities may lengthen overall recovery time. 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. Recovery Manager optimizes local repair of data failures using local backups. 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 . Data Recovery Advisor diagnoses persistent (on disk) data failures, presents appropriate repair options, and runs repair operations at your request. If the primary system should fail, the first standby database becomes the new primary database. Footnote3For qualified one-off patches only. Split brain syndrome occurs when the instances in a RAC fails to connect or ping to each other via the private interconnect, Although the servers are physically up and running and the database instances on these servers is also running. Maximum RTO for data corruptions, database, or site failures is in seconds to minutes. Oracle GoldenGate is optimized for replicating data. Provides the simplicity of a physical replica. Note, however, that the synchronous redo transport does not impose any physical distance limitation. 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. Longer detection time usually leads to longer recovery time required to repair the appropriate transactions. Nodes 1,2 can talk to each other. Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. Hence, we observed that when an equal number of database services were running on both nodes, the node with lower node number (host01) survives. Footnote1Rolling upgrades with Oracle Clusterware and Oracle RAC incur zero downtime. Online Patching allows for dynamic database patching of typical diagnostic patches. You should determine if both sites are likely to be affected by the same disaster. Table 7-5 compares the attainable recovery times of each Oracle high availability architecture for all types of planned downtime. Thus, compared to Oracle Data Guard, a remote mirroring solution must transmit each change many more times to the remote site. Oracle RAC Operational Best Practices for the Cloud Created Date: Vijay.Cherukuri-Oracle Dec 18 2011 edited Nov 5 2012. An architecture that combines Oracle Database with Oracle RAC is inherently a highly available system. 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. During normal operation, the production site services requests; in the event of a site failover or switchover, the standby site takes over the production role and all requests are routed to that site. If your business does not require the scalability and additional high availability benefits provided by Oracle RAC, but you still need all the benefits of Oracle Data Guard and cold cluster failover, then Oracle Database with Oracle Clusterware and Oracle Data Guard is a good compromise architecture. During the process of resolving conflicts, information may be lost or become corrupted. Oracle Data Guard is designed to allow businesses get something useful out of their expensive investment in a disaster-recovery site. 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. Automatic block repair may be possible, thus eliminating any downtime in an Oracle Data Guard configuration. This functionality is available starting with Oracle Database 11g Release 2 (11.2.0.2). Online Application Maintenance and Upgrades with Edition-based redefinition allows an application's database objects to be changed without interrupting the application's availability, Automatic and fast failover for computer failure, Minimum rolling upgrade capabilities for system, clusterware, and operating systemFootref1, High availability, scalability, and foundation of server database grids, Automatic recovery of failed nodes and instances, Fast application notification (FAN) with integrated Oracle client failover, FAN with integrated Oracle client failover for pooled resources and third-party vendor middle tiers. For example, if the primary database fails over to one of the standby databases in the Data Guard hub, the new primary database acquires more system and storage resources while the testing resources may be temporarily starved. Disaster strikes the primary database, and its network connections to both the observer and the target standby database are lost. Oracle GoldenGate can capture data changes at the primary database or downstream at a replica database, thus enabling users to build hub-and-spoke network configurations that can support hundreds of replica databases. You can have up to 32 voting disks in your cluster. More investment and expertise to build and maintain an integrated high availability solution is available. Oracle Database High Availability Architectures, Choosing the Correct High Availability Architecture, Integrating Application Server High Availability, Integrating High Availability for All Applications. If the sub-clusters are of the different sizes, the functionality is same as earlier i.e. 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. For physical standby databases, this solution: Supports very high primary database throughput. Then this process is referred as Split Brain Syndrome. which node first joined the cluster). Simulate loss of connectivity between two nodes. 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. Their strategy further mitigates risk by maintaining multiple standby databases, each implemented using a different architecturesRedo Apply and SQL Apply. The SELECT statement is used to retrieve information from a database. Building on top of the local high availability solutions is the Oracle Application Server disaster recovery solution. Flexible and automated high availability solutions ensure that applications you deploy on Oracle Application Server meet the required availability to achieve your business goals. Split Brain: Whats new in Oracle Database 12.1.0.2c? Ina cluster, a private interconnect is used by cluster nodes to monitor each nodes status and communicate with each other. . By using specialized devices, this distance can be extended to 66 kilometers. 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. The system resources can be dynamically allocated and deallocated depending on various priorities. Footnote2Oracle ASM automatically rebalances stored data when disks are added or removed while the database remains online. Then there are two cohorts: {1, 2} and {3}. Figure 7-6 Primary and Standby Databases and the Observer During Fast-Start Failover. See Section 7.2 for a comparison of the different architectures and highlights of the benefits and considerations. A highly available and resilient application requires that every component of the application must tolerate failures and changes. 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 . 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. 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. The voting result is similar to clusterware voting result. (See Section 7.1.5 for a complete description.). Oracle Clusterware provides tolerance of node failures, whereas Oracle Data Guard provides additional protection against data corruptions, lost writes, and database and site failures. Oracle GoldenGate can capture changes at a source database, and the captured changes can be propagated asynchronously to replica databases. 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. For storage migration, you are required to use both storage arrays by Oracle ASM temporarily. 2. As a result, equal number of database services execute on both the nodes. The rightmost frame shows the configuration after fast-start failover has occurred. Online Application Maintenance and Upgrades with Edition-based redefinition allows an application's database objects to be changed without interrupting the application's availability. (The application server on the secondary site can be active and processing client requests such as queries if the standby database is a physical standby database with the Active Data Guard option enabled, or if it is a logical standby database.). Oracle Clusterware provides a number of benefits over third-party clusterware. Oracle RAC Split Brain Syndrome Scenerio. Split Brain Syndrome Basic Concept in Oracle RAC. 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. Maximum RTO for instance or node failure is in seconds to minutes. Filed Under: oracle, RAC Tagged With: RAC, split brain, vcs basics Communication faults, jeopardy, split brain, I/O fencing, How to Enable or Disable Veritas ODM for Oracle database 12.1.0.1, ORA-16713: The Oracle Data Guard broker command timed out When Changing LogXptMode, Managing Oracle Database Backup with RMAN (Examples included), Cron Script does not Execute as Expected from crontab Troubleshoot, Oracle SQL Script to Report Tablespace Free and Fragmentation, Beginners Guide to Flash Recovery Area in Oracle Database, How to Identify the Last and Next Refresh Dates for a Materialized View, Oracle 20c New Feature: PDB Point-in-Time Recovery or Flashback to Any Time, How to use nomodeset to Troubleshoot Boot Issues. 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. You can configure the failed application connections to fail over to the replica. High availability solution with added data and disaster recovery protection. 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 . See Section 1.5, "Roadmap to Implementing the Maximum Availability Architecture (MAA)" for more information about the best practices documentation. Oracle Data Guard provides more comprehensive data protection and its more efficient network usage allows plenty of room to grow without the expense of upgrading its network. Oracle Database with Oracle GoldenGate provides granularity and control over what is replicated and how it is replicated. Split Brain Syndrome in RAC. Higher flexibilityOracle Data Guard is implemented on pure commodity hardware. 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. Oracle Data Guard transmits redo data from the primary database to the secondary site to keep the databases synchronized. Oblivious of the existence of other cluster fragments, each sub-cluster continues to operate independently of the others. 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. This private network interface or interconnect are redundant and are only used for inter-instance oracle data block transfers. Clients are connected to the logical standby database and can work with its data. Any database in a Data Guard configuration, whether a primary or standby database, can be an Oracle One Node database. You can configure Oracle GoldenGate with Oracle Data Guard to provide protection for the individual databases in the configuration. Node 1 is connected to Node 2 and to the Oracle database, but Node 1 is currently idle, in standby mode. What is split brain in Oracle RAC? 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 RAC on an extended cluster provides greater availability than a local Oracle RAC cluster, but an extended cluster may not completely fulfill the disaster recovery requirements of your organization. Figure 7-2 Oracle Database with Oracle Clusterware (Before Cold Cluster Failover). 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. The Maximum Availability Architecture (MAA) is Oracle's best practices blueprint. To ensure data consistency, each instance of a RAC database needs to keep heartbeat with the other instances.
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