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). Oracle Secure Backup provides a centralized tape backup management solution. If the fast recovery area is on the source volume that is remotely mirrored, then you must also remotely mirror the flashback logs. 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. Figure 7-6 shows the relationships between the primary database, target standby database, and the observer before, during, and after a fast-start failover. 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 . Footnote6Recovery time for human errors depend primarily on detection time. 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. 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. host01 is evicted although it has a lower node number. 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. 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. Logical or user failures that manipulate logical data (DMLs and DDLs). Different character sets are required between the primary database and its replicas. Many high availability architectures today use clusters alone to provide some rudimentary node redundancy and automatic node failover. However, if a remote mirroring solution is used for data protection, typically you must mirror the database files, the online redo log, the archived redo logs, and the control file. The production database is connected over the network to the physical standby database site and the logical standby database site (the standby databases may be at the same or different sites). What Is Oracle RAC. Please enroll for the Oracle DBA Interview Question Course.https://learnomate.org/courses/oracle-dba-interview-question/Use DBA50 to get 50% discountPlease s. Fast Recovery Area manages local recover-related files automatically. Whatever the case, these Oracle RAC interview questions and answers are for you. Thus, when a failover occurs, you can prioritize the system resources to production activity and allocate new system resources in a grid for the standby database functions. Uses a private network and voting disk-based communication to detect and resolve split-brain Foot 2 scenarios. the clusterware identifies the largest sub-cluster, and aborts all the nodes which do. Maximum RTO for instance or node failure is in minutes. Oracle RAC Split Brain Syndrome Scenerio. The following sections provide an overview of Oracle Database high availability architectures and implement the MAA best practices: Oracle Database with Oracle Clusterware (Cold Cluster Failover), Oracle Database with Oracle Real Application Clusters (Oracle RAC), Oracle Database with Oracle Clusterware and Oracle Data Guard, Oracle Database with Oracle RAC One Node and Oracle Data Guard, Oracle Database with Oracle RAC and Oracle Data Guard. Oracle Data Guard Advantages Compared to Remote Mirroring Solutions. 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. Evaluate logical standby databases if additional indexes are required for reporting purposes and if your application only uses data types supported by logical standby database and SQL Apply. But 1 and 2 cannot talk to 3, and vice versa. Oracle Clusterware: Enables you to use an entire software solution from Oracle, avoiding the cost and complexity of maintaining additional cluster software. Oracle Database High Availability Architectures, Choosing the Correct High Availability Architecture, Integrating Application Server High Availability, Integrating High Availability for All Applications. The rightmost frame shows the configuration after fast-start failover has occurred. The active site is generally called the production site, and the passive site is called the standby site. 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. Split Brain Syndrome: In a Oracle RAC environment all the instances/servers communicate with each other using high-speed interconnects on the private network. Oracle GoldenGate is optimized for replicating data. If the sub-clusters are of the different sizes, the functionality is same as earlier i.e. 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. Because Oracle Data Guard only propagates the redo data in the logs, and the log file consistency is checked before it is applied, all such external corruptions are eliminated by Oracle Data Guard. RAC Split Brain Syndrome. Table 7-5 Attainable Recovery Times for Planned Outages, System change - Dynamic Resource Provisioning. Although cold cluster failover is not shown in Figure 7-8, you can configure it by adding a passive node on the secondary site. Clients on the network experience a period of lockout while the failover occurs and are then served by the other database instance after the instance has started. Maximum RTO for instance or node failure is zero for the databaseFootref1. Now talking about split-brain concept with respect to oracle RAC systems, it occurs when the instance In addition to maintaining its own disk block, CSSD processes also monitors the disk blocks maintained by the CSSD processes running in other cluster nodes. There is no fancy or expensive hardware required. Willing to make additional provisions for remote data protection to protect against database, data, and cluster failures and corruptions. Use a physical standby database if read-only access is sufficient. 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. Provides read-only access to synchronized standby database and fast incremental backups to off-load production. 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. Where two or more instances . 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. Limited support for mixed platforms. Following the execution of a SELECT statement, a tabular result is held in a result table (called a result set). 2. 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. Thus, compared to Oracle Data Guard, a remote mirroring solution must transmit each change many more times to the remote site. 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)), Zero downtime with Grid Control provisioning, Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patchesFoot1, Database Grid with site failure protection, Simplest high availability, data protection, and disaster-recovery solution, Automatic and fast failover for computer failure, storage failure, data corruption, for configured ORA- errors or conditions and database failures, Rolling upgrade for system, clusterware, database, and operating systemFoot2, Ability to off-load backups to the standby database, Ability to off-load read and reporting workload to the standby database. The split brain syndrome and its affects and how it has been managed in oracle is mentioned below. This has the potential for data corruption. All Oracle RAC nodes can be active by implementing multiple Oracle RAC One Node configurations for different databases. split brain syndrome. 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. Footnote5Storage failures are prevented by using Oracle ASM with mirroring and its automatic rebalance capability. Section 7.1.8 describes how you can achieve the highest level of availability with Oracle RAC and Oracle Data Guard. Oracle Flashback Technology optimizes logical failure repair. Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. Network connection changes and other site-specific failover activities may lengthen overall recovery time. Hello Friends,Welcome you back on exciting topic, today's session is onNode Membership || Voting Disk || Split Brain Syndrome in Oracle RAC - Real Applicatio. 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. The production database transmits redo data (either synchronously or asynchronously) to redo log files at the physical standby database. Also, for large data centers with a need to support many applications with Oracle Data Guard requirements, you can build an Oracle Data Guard hub to reduce the total cost of ownership. Oracle Enterprise Manager support for patch application simplifies software maintenance. If your VM is sized too small, you can migrate the Oracle RAC One instance to another larger Oracle VM node in the cluster (using the online database relocation utility) or move the Oracle RAC One instance to another Oracle VM node, and then resize the Oracle VM. The logical standby database may contain additional indexes and materialized views. By reducing the combinations of software that you must coordinate and support, you can increase the manageability and availability of your system software. The instances monitor each other by checking "heartbeats." 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. 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. The heartbeat is maintained by background processes like LMON, LMD, LMS and LCK. Network addresses are failed over to the backup node. In a split brain situation, voting disk is used to determine which node(s) will survive and which node(s) will be evicted. Then, the redo data is applied from the logs to the physical standby database, which backs up the redo data to physical media. This is often called the multi-master problem. Unlike the cold cluster model where one node is completely idle, all instances and nodes can be active to scale your application. Oracle Database with Oracle RAC architecture is designed primarily as a scalability and availability solution that resides in a single data center. Figure 7-2 shows a configuration that uses Oracle Clusterware to extend the basic Oracle Database architecture and provide cold cluster failover. Oblivious of the existence of other cluster fragments, each sub-cluster continues to operate independently of the others. For physical standby databases, this solution: Supports very high primary database throughput. Oracle RAC Split Brain Syndrome Scenerio. 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. Note, however, that the synchronous redo transport does not impose any physical distance limitation. 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. 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. You can have up to 32 voting disks in your cluster. Automatic block repair may be possible, thus eliminating any downtime in an Oracle Data Guard configuration. The center frame shows the configuration during fast-start failover. 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 Data Guard Advantages Over Traditional Solutions. 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 . This section contains the following topics: Oracle Application Server High Availability Architectures, High Availability Services in Oracle Application Server. These devices convert ESCON or Fibre Channel to the appropriate IP, ATM, or SONET networks. In a split brain situation, voting disk will be used to determine which node(s) survive and which node(s) will be evicted. With Oracle RAC integration, database scalability is possible. The cold cluster failover solution with Oracle Clusterware provides these additional advantages over a basic database architecture: Automatic recovery of node and instance failures in minutes, Automatic notification and reconnection of Oracle integrated clientsFoot3, Ability to customize the failure detection mechanism. In Oracle RAC, all the instances/servers communicate with each other using a private network. This chapter describes the various high availability architectures in an Oracle environment and helps you to choose the correct architecture for your organization.