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. These redundant configurations provide increased availability either through a distributed workload, through a failover setup, or both. Table 7-2 High Availability Architecture Recommendations. To provide this transparent failover capability, Oracle Clusterware requires a virtual IP (VIP) address for each node in the cluster. 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. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. Oracle RAC Split Brain Syndrome Scenerio oracle-tech The public and private interconnects, and the Storage Area Network (SAN) are all on separate dedicated channels, with each one configured redundantly. The data is derived from actual user experiences and from Oracle service requests. Oracle Database with Oracle GoldenGate provides granularity and control over what is replicated and how it is replicated. But 1 and 2 cannot talk to 3, and vice versa. Q39) Mention what is split brain syndrome in RAC? More investment and expertise to build and maintain an integrated high availability solution is available. Simulate loss of connectivity between two nodes. This section summarizes the advantages of the different high availability architectures and provides guidelines for you to choose the correct high availability architecture for your business. To ensure data consistency, each instance of a RAC database needs to keep heartbeat with the other instances. Typically, this is not possible with remote mirroring solutions. 817202 Mar 1 2016 edited Mar 2 2016. What Is Oracle RAC. Footnote8With automatic block repair, this should be the most common block corruption repair. Oracle RAC Split Brain Syndrome Scenerio. You might choose to use Oracle GoldenGate to configure and maintain a logical copy of your production database. This architecture is referred to as an extended cluster. Start both the services for database admindb so that equal number of database services execute on both the nodes. The figure shows Oracle Database with Oracle Data Guard architecture. 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). 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. See Oracle Data Guard Broker for a detailed description of the observer. Figure 7-3 Oracle Database with Oracle Clusterware (After Cold Cluster Failover). (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. Footnote3Recovery time consists largely of the time it takes to restore the failed system. Split Brain Syndrome: In a Oracle RAC environment all the instances/servers communicate with each other using high-speed interconnects on the private network. Footnote1Rolling upgrades with Oracle Clusterware and Oracle RAC incur zero downtime. 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. Rolling upgrade for system, clusterware, database, and operating system. Oblivious of the existence of other cluster fragments, each sub-cluster continues to operate independently of the others. The premise of the Data Guard hub is that it provides higher utilization with lower cost. Online Patching allows for dynamic database patches for diagnostic and interim patches. For availability reasons, the Oracle database is a single database that is mirrored at both of the sites. 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)). 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. After you have chosen an architecture, then implement it using the operational and configuration best practices described in the MAA white papers and in Oracle Database High Availability Best Practices. For example, you can put the files on different disks, volumes, file systems, and so on. A highly available and resilient application requires that every component of the application must tolerate failures and changes. At the logical standby database, the redo data is transformed into SQL statements, which are applied to the logical standby database. Better functionalityOracle Data Guard provides full suite of data protection features that provide a much more comprehensive and effective solution optimized for data protection and disaster recovery than remote mirroring solutions. You can achieve the highest level of availability when using Oracle RAC and Oracle Data Guard and there is no need to make application changes to use these Oracle Database features. During the process of resolving conflicts, information may be lost or become corrupted. In this article I will explore this new feature for one of the possible factors contributing to the node weight, i.e. Fast-Start Fault Recovery bounds and optimizes instance and database recovery times to minutes. 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. 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. By reducing the combinations of software that you must coordinate and support, you can increase the manageability and availability of your system software. High availability solution with added data and disaster recovery protection. 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. What is split brain in RAC? - TheNewsIndependent With Oracle Clusterware, . sub-clusters are of equal size, I have shut down one of the nodes so that there are only 2 active nodes in the cluster. 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. 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. The database consists of a collection of data files, control files, and redo logs located on disk. Support for fine-grained, n-way multimaster, hub-and-spoke, or many-to-one replication architectures. Additional protection from data center failure with special considerations that are documented in Section 7.1.4.1, Highest level of availability for server or computer room failure. Online Application Maintenance and Upgrades with Edition-based redefinition allows an application's database objects to be changed without interrupting the application's availability. 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. With either the active-active or the active-passive category, multiple solutions exist that differ in ease of installation, cost, scalability, and security. Oracle RAC One Node allows you to run one instance of an Oracle RAC database on a single node in a cluster. Better suited for WANsRemote mirroring solutions based on storage systems often have a distance limitation due to the underlying communication technology (Fibre Channel or ESCON (Enterprise Systems Connection)) used by the storage systems. Table 7-3 Additional Capabilities of High Level Oracle High Availability Architectures, The foundation for all high availability architectures. Chapter 2 describes how the high availability requirements for the business plus its allotted budget determine the appropriate architecture. If the sub-clusters are of the different sizes, the clusterware identifies the largest sub-cluster, and aborts all the nodes which do. PDF Key Technical Features of Oracle RAC 12c For example : Flexible and automated high availability solutions ensure that applications you deploy on Oracle Application Server meet the required availability to achieve your business goals. 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. Footnote1Recovery time indicated applies to database and existing connection failover. c. Some improvement has been made to ensure node(s) with lower load survive in case the eviction is caused by high system load. The individual nodes are running fine and can accept user connections and work . Footnote5Storage failures are prevented by using Oracle ASM with mirroring and its automatic rebalance capability. Automatic block repair may be possible, thus eliminating any downtime in an Oracle Data Guard configuration. Oracle RAC Interview Questions - Coherence and Split-Brain Oracle Clusterware provides a number of benefits over third-party clusterware. Split Brain Resolution in Oracle Clusterware 12c Rel 2 1. Vijay.Cherukuri-Oracle Dec 18 2011 edited Nov 5 2012. The new primary database starts transmitting redo data to the new standby database. The system resources can be dynamically allocated and deallocated depending on various priorities. Oracle Clusterware manages the availability of both the user applications and Oracle databases. Network addresses are failed over to the backup node. The common voting result will be: a. 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. In a split brain situation, voting disk is used to determine which node(s) will survive and which node(s) will be evicted. Maximum RTO for instance or node failure is zero for the databaseFootref1. Split Brain Condition - STOMITH STONITH fencing - dba-oracle.com Uses a private network and voting disk-based communication to detect and resolve split-brain Foot 2 scenarios. 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. Figure 7-2 shows a configuration that uses Oracle Clusterware to extend the basic Oracle Database architecture and provide cold cluster failover. The voting result is similar to clusterware voting result. Each instance is associated with a service: HR, Sales, and Call Center. 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. Then this process is referred as Split Brain Syndrome. 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. If the sub-clusters are of the different sizes, the functionality is same as earlier i.e. What is Voting Disk & Split Brain Syndrome in RAC the number of database services executing on a node. Split Brain Syndrome Basic Concept in Oracle RAC High availability functionality to manage third-party applications, Rolling release upgrades of Oracle Clusterware. 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 . Split Brain: Whats new in Oracle Database 12.1.0.2c? It is based on proven Oracle high availability technologies and recommendations. Figure 7-9 Oracle Database with Oracle RAC and Oracle Data Guard - MAA. Oracle Database is a single-instance, standalone (noncluster) database and it is the foundation for all high availability architectures. 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. 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. Any database in a Data Guard configuration, whether a primary or standby database, can be an Oracle One Node database. Oracle RAC Split Brain Syndrome Scenerio - Oracle Forums 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. Oracle Database with Oracle RAC architecture provides the following benefits over a traditional monolithic database server and the cold cluster failover model: Flexibility to increase processing capacity using commodity hardware without downtime or changes to the application, Ability to tolerate and quickly recover from computer and instance failures (measured in seconds), Optimized communication in the cluster over redundant network interfaces, without using bonding or other technologies. Controlfile is used similarly to voting disk in clusterware layer to determine which instance(s) survive and which instance(s) evict. Now talking about split-brain concept with respect to oracle RAC systems, it occurs when the instance By using specialized devices, this distance can be extended to 66 kilometers. Suppose there are 3 nodes in the following situation. Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patches. Since I will only explore the scenarios for which functionality has been modified, i.e. In Oracle RAC, all the instances/servers communicate with each other using a private network. Oracle RAC builds higher levels of availability on top of the standard Oracle Database features. Oracle Secure Backup provides a centralized tape backup management solution. 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. It also allows the storage to be laid out in a different fashion from the primary computer. Another possible configuration might be a testing hub consisting of snapshot standby databases. RAC Split Brain Syndrome - Devops Tutorials 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. A single standby database architecture consists of the following key traits and recommendations: Standby database resides in Site B. For example, you can use your favorite application query in the database check action. Table 7-2 recommends architectures based on your business requirements for RTO, RPO, MO, scalability, and other factors. Support is for single-instance databases only. Where two or more instances . 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. Footnote4Tables can be reorganized online using the DBMS_REDEFINITION package. Oracle Application Server provides redundancy by offering support for multiple instances supporting the same workload. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). 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. 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. 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. 2. In a non-RAC Oracle database, a single instance accesses a single database. This book focuses primarily on the database high availability solutions. As the result, 1 or more instance(s) will be evicted. 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. Willing to make additional provisions for remote data protection to protect against database, data, and cluster failures and corruptions. Oracle Flashback Technology optimizes logical failure repair. Network connection changes and other site-specific failover activities may lengthen overall recovery time. However, the online changes are not supported by SQL Apply or data capture, and therefore the effects of this subprogram are not visible on the logical standby database or replica database. 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. Customer can designate which server(s) and resource(s) are critical 2. Use a physical standby database if read-only access is sufficient. For example, Table 7-1 provides some insight into the probability of different outages during unplanned and planned activities. Suppose there are 3 nodes in the following situation. Although using Oracle GoldenGate might require additional work, it offers increased flexibility that might be necessary to meet specific business requirements. 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. As per Split brain syndrome in Oracle RAC in case of inter-connect failures the master node will evict other/dead nodes . 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. 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. This is often called the multi-master problem. An Oracle RAC extended cluster is an architecture that provides extremely fast recovery from a site failure and allows for all nodes, at all sites, to actively process transactions as part of single database cluster. If you configure a single voting disk, then you should use external mirroring to provide redundancy. At the time of role transition, more storage and system resources can be allocated toward that application. The observer (thin client watchdog) resides in the application tier and monitors the availability of the primary database. 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. With Oracle RAC integration, database scalability is possible. 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 . These figures show how you can use the Oracle Clusterware framework to make both Oracle Database and your custom applications highly available. 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. 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 Data Guard transmits redo data from the primary database to the secondary site to keep the databases synchronized. For virtualization, Oracle RAC One Node with Oracle VM increases the benefit of Oracle VM with the high availability and scalability of Oracle RAC. 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. host02 is retained as it has higher number of database services executing. Figure 7-9 shows the recommended MAA configuration, with Oracle Database, Oracle RAC, and Oracle Data Guard. 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. Uses a private network and voting disk-based communication to detect and resolve split-brainFoot2 scenarios. Oracle Enterprise Manager support for patch application simplifies software maintenance. High availability benefits and workload balancing outweigh performance concerns. 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 .