Corruption Prevention, Detection, and Repair detect and prevent some corruptions and lost writes. Split Brain in RAC Database | RAC DBA Training - YouTube Oracle RAC Operational Best Practices for the Cloud Created Date: Table 7-4 shows the recovery time (including detection and client failover time) of an integrated Oracle client, whenever relevant. In Oracle RAC each node in the cluster is interconnected through a private interconnect. 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. The rightmost frame shows the configuration after fast-start failover has occurred. 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. Nodes 1,2 can talk to 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. Any of these processes experience IPC Send time out will incur communication reconfiguration and instance eviction to avoid split brain. A highly available and resilient application requires that every component of the application must tolerate failures and changes. Footnote7Recovery time depends on block media recovery and the time it takes to restore a consistent block from the flashback logs or database backups, and to recover the block by applying all the redo from archive logs and online redo logs. Typically, this is not possible with remote mirroring solutions. The figure shows Oracle Database with Oracle Data Guard architecture. The SELECT statement is used to retrieve information from a database. Customer can designate which server(s) and resource(s) are critical 2. Furthermore, the standby databases can be used for read-only access and subsequently for reader farms, for reporting, and for testing and development. If it takes seconds to detect a malicious DML or DLL transaction, it typically only requires seconds to flash back the appropriate transactions. This configuration consists of a central resource supporting 10 applications and databases in the grid, rather than managing 10 separate system or storage units in a nongrid infrastructure. host02 is retained as it has higher number of database services executing. host01 is evicted although it has a lower node number. the number of database services executing on a node. The new primary database starts transmitting redo data to the new standby database. To ensure data consistency, each instance of a RAC database needs to keep heartbeat with the other instances. 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. 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. The instances monitor each other by checking "heartbeats." 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. It supports bidirectional replication, data transformations, subsetting, custom apply functions, and heterogeneous platforms. An infrastructure services provider to the telecommunication industry uses a single standby database located over 400 miles away from the primary database configured for synchronous redo transport, enabling zero-data-loss failover for maximum data protection and high availability. the clusterware identifies the largest sub-cluster, and aborts all the nodes which do. The database consists of a collection of data files, control files, and redo logs located on disk. c. Some improvement has been made to ensure node(s) with lower load survive in case the eviction is caused by high system load. Network addresses are failed over to the backup node. Online Reorganization and Redefinition allows for dynamic data changes. Online Patching allows for dynamic database patches for diagnostic and interim patches. 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. 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. Data Recovery Advisor provides intelligent advice and repair of different data failures, Oracle Secure Backup provides a centralized tape backup management solution. 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. Figure 7-6 shows the relationships between the primary database, target standby database, and the observer before, during, and after a fast-start failover. Now talking about split-brain concept with respect to oracle RAC systems, it occurs when the instance You might choose to use Oracle GoldenGate to configure and maintain a logical copy of your production database. For example, you can use your favorite application query in the database check action. 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/. 2. During the process of resolving conflicts, information may be lost or become corrupted. Oracle Clusterware provides tolerance of node failures, whereas Oracle Data Guard provides additional protection against data corruptions, lost writes, and database and site failures. 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. 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. SELECT statements might be as straightforward as selecting a few . Split Brain Syndrome Basic Concept in Oracle RAC This functionality is available starting with Oracle Database 11g Release 2 (11.2.0.2). Oracle RAC Split Brain Syndrome Scenerio - Oracle Forums 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. We will verify that when an equal number of database services are running on both nodes, the node with lower node number (host01) survives. For physical standby databases, this solution: Supports very high primary database throughput. The Maximum Availability Architecture (MAA) is Oracle's best practices blueprint. Fast-start failover is recommended to provide automatic failover without user intervention and bounded recovery time. 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. Now talking about split-brain concept with respect to oracle . 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. There is no fancy or expensive hardware required. All Oracle RAC nodes can be active by implementing multiple Oracle RAC One Node configurations for different databases. 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 split brain syndrome and its affects and how it has been managed in oracle is mentioned below. mysql - Split brain scenario - RAC and PXC - Database Administrators More investment and expertise to build and maintain an integrated high availability solution is available. The individual nodes are running fine and can accept user connections and work . Split Brain Resolution in Oracle Clusterware 12c Rel 2 1. Traditionally, Oracle RAC is used in a multinode architecture, with many separate database instances running on separate servers. Uses a private network and voting disk-based communication to detect and resolve split-brain Foot 2 scenarios. The observer (thin client watchdog) resides in the application tier and monitors the availability of the primary database. Oracle Flashback Technology optimizes logical failure repair. Table 7-2 recommends architectures based on your business requirements for RTO, RPO, MO, scalability, and other factors. 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. In Oracle RAC, all the instances/servers communicate with each other using a private network. 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. Support for bidirectional replication and updating anything and anywhere. 1. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). Each instance is associated with a service: HR, Sales, and Call Center. . 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. Building on top of the local high availability solutions is the Oracle Application Server disaster recovery solution. Split Brain Syndrome | Oracle Database Internal Mechanism For example, if the extended cluster configuration is set up properly, it can protect against disasters such as a local power outage, an airplane crash, or a flooded server room. 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. But 1 and 2 cannot talk to 3, and vice versa. What is split brain in RAC? - TheNewsIndependent The heartbeat is maintained by background processes like LMON, LMD, LMS and LCK. Limited support for mixed platforms. For more information about constructing multiple-source replication environments, see the Oracle GoldenGate documentation. At the logical standby database, the redo data is transformed into SQL statements, which are applied to the logical standby database. Maximum RTO for data corruptions, database, or site failures is in seconds to minutes. Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. 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. 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 ). Simulate loss of connectivity between two nodes. See the high availability solutions and recommendations for Oracle Application Server, Oracle Enterprise Manager, and Oracle Applications on the MAA Web site at: Oracle Database High Availability Best Practices, Oracle Real Application Clusters Administration and Deployment Guide, Oracle Data Guard Concepts and Administration, Oracle Streams Replication Administrator's Guide, Oracle Fusion Middleware High Availability Guide, Oracle Application Server High Availability Guide, Section 1.5, "Roadmap to Implementing the Maximum Availability Architecture (MAA)", Corruption Prevention, Detection, and Repair, Online Application Maintenance and Upgrades, Description of "Figure 7-1 Single-Node, Nonclustered Oracle Database with an Oracle ASM Instance", Section 7.1.3, "Oracle Database with Oracle RAC One Node", Description of "Figure 7-2 Oracle Database with Oracle Clusterware (Before Cold Cluster Failover)", Description of "Figure 7-3 Oracle Database with Oracle Clusterware (After Cold Cluster Failover)", Description of "Figure 7-4 Oracle Database with Oracle RAC Architecture", Description of "Figure 7-5 Oracle RAC Extended Cluster", http://www.oracle.com/technetwork/database/clustering/overview/, Description of "Figure 7-6 Primary and Standby Databases and the Observer During Fast-Start Failover", Description of "Figure 7-7 Oracle Database with Oracle Data Guard on Primary and Multiple Standby Sites", Description of "Figure 7-8 Oracle Clusterware (Cold Cluster Failover) and Oracle Data Guard", Description of "Figure 7-9 Oracle Database with Oracle RAC and Oracle Data Guard - MAA". 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. 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. 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 more information, see the "Administering Oracle RAC One Node" section in the Oracle Real Application Clusters Administration and Deployment Guide. Then this process is referred as Split Brain Syndrome. Fast Recovery Area manages local recover-related files automatically. Site configurations are on heterogeneous platforms. What Is Oracle RAC. This architecture is the recommended configuration for Maximum Availability Architecture (MAA). 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. Also, to prevent a full cluster outage if either site fails, the configuration includes a third voting disk on an inexpensive, low-end standard network file system (NFS) mounted device. The operation of an Oracle Clusterware cold cluster failover is depicted in Figure 7-2 and Figure 7-3. This private network interface or interconnect are redundant and are only used for inter-instance oracle data block transfers. New requests are accepted after the Split-Brain event and then performed on potentially corrupted system state (thus potentially corrupting system state even further). High availability functionality to manage third-party applications, Rolling release upgrades of Oracle Clusterware. 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 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. When the processes of the distributed system rejoin together it is possible that they have conflicting views of system state or resource ownerships. What is split brain in Oracle RAC? This figure shows Oracle Database with Oracle RAC architecture for a partitioned three-node database. Vijay.Cherukuri-Oracle Dec 18 2011 edited Nov 5 2012. Maximum RTO for instance or node failure is in seconds to minutes. Hello Friends,Welcome you back on exciting topic, today's session is onNode Membership || Voting Disk || Split Brain Syndrome in Oracle RAC - Real Applicatio. 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 group(cohort) with lower node member survive, in case of same number of node(s) available in each group. Split Brain: What's new in Oracle Database 12.1.0.2c? Footnote8With automatic block repair, this should be the most common block corruption repair. Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patches. Ina cluster, a private interconnect is used by cluster nodes to monitor each nodes status and communicate with each other. 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. Flexible propagation and management of data, transactions, and events. There are numerous high availability features that you can use in the Oracle Database single-instance database architecture. High availability benefits and workload balancing outweigh performance concerns. 2. Split Brain Syndrome Basic Concept in Oracle RAC. Footnote2Oracle ASM automatically rebalances stored data when disks are added or removed while the database remains online. Footnote3The initial investment to build a robust solution is well worth the long-term flexibility and capabilities that Oracle GoldenGate delivers to meet specific business requirements. Section 7.1.8 describes how you can achieve the highest level of availability with Oracle RAC and Oracle Data Guard. If the sub-clusters have unequal node weights, the sub-cluster having the higher weight survives so that, in a 2-node cluster, the node with the lowest node number might be evicted if it has a lower weight. 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. Recovery Manager (RMAN) optimizes local repair of data failures. 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. In previous releases, technologies like bonding or trunking were used to make use of redundant networks for the interconnect. Longer detection time usually leads to longer recovery time required to repair the appropriate transactions. 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. Oracle RAC Split Brain Syndrome Scenerio oracle-tech Higher ROIBusinesses must obtain maximum value from their IT investments, and ensure that no IT infrastructure is sitting idle. These best practices are required to maximize the benefits of each architecture. 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. Provides seamless integration with, and migration to, Oracle Real Application Clusters (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 . The key factors include: Recovery time objective (RTO) and recovery point objective (RPO) for unplanned outages and planned maintenance, Total cost of ownership (TCO) and return on investment (ROI). As per Split brain syndrome in Oracle RAC in case of inter-connect failures the master node will evict other/dead nodes . Start both the services for database admindb so that serv1 executes on host01 and serv2 executes on host02. 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. Whatever the case, these Oracle RAC interview questions and answers are for you. The application VIP is tied to the application by making it dependent on the application resource defined by Cluster Ready Services (CRS). The premise of the Data Guard hub is that it provides higher utilization with lower cost. There are three typical causes of corruption: 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. You can configure Oracle GoldenGate with Oracle Data Guard to provide protection for the individual databases in the configuration. Hi Guru's. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). 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. The active site is generally called the production site, and the passive site is called the standby site. Applications can easily mask failures to the end user. The processes that were once co-operating prior to the Split-Brain event occurring, independently modify the same logically shared state, thus leading to conflicting views of system state. (See Section 7.1.5 for a complete description.). 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. 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 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 . This scenario enables the provider to use existing data centers that are geographically isolated, offering a unique level of high availability. For example, you can put the files on different disks, volumes, file systems, and so on. For more information, see Oracle Data Guard Concepts and Administration or the Oracle Streams Replication Administrator's Guide.
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