Oracle RAC Split Brain Syndrome Scenerio. Also, see Figure 5-2 for another example of a multiple standby database environment. b. Suppose there are 3 nodes in the following situation. But 1 and 2 cannot talk to 3, and vice versa. Different character sets are required between the primary database and its replicas. 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. The second standby database automatically receives data from the new primary database, insuring that data is protected at all times. Footnote1Applications (or a portion of an application) connected to the system that is being maintained may be temporarily affected. Oracle Clusterware provides a number of benefits over third-party clusterware. This private network interface or interconnect are redundant and are only used for inter-instance oracle data block transfers. 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. After the former primary database has been repaired, the observer reestablishes its connection to that database and reinstates it as a new standby database. 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. 1. The solutions introduced in this book are described in detail in the Oracle Fusion Middleware High Availability Guide. Footnote4Database is still available, but a portion of the application connected to the failed system is temporarily affected. 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. Split Brain Syndrome in RAC. Uses a private network and voting disk-based communication to detect and resolve split-brain Foot 2 scenarios. All of the business benefits of Oracle RAC. Split Brain Resolution in Oracle Clusterware 12c Rel 2 1. There are three typical causes of corruption: This chapter describes the various high availability architectures in an Oracle environment and helps you to choose the correct architecture for your organization. Figure 7-6 Primary and Standby Databases and the Observer During Fast-Start Failover. Rolling upgrades for system and hardware changes, Rolling patch upgrades for some interim patches, security patches, CPUs, and cluster software, Fast, automatic, and intelligent connection and service relocation and failover, Comprehensive manageability integrating database and cluster features with Grid Plug and Play and policy-based cluster and capacity management, Load balancing advisory and run-time connection load balancing help redirect and balance work across the appropriate resources. The premise of the Data Guard hub is that it provides higher utilization with lower cost. Oracle Automatic Storage Management and Oracle Automatic Storage Management Cluster File System (Oracle ACFS) tolerate storage failures and optimize storage performance and utilization. If the fast recovery area is on the source volume that is remotely mirrored, then you must also remotely mirror the flashback logs. See Section 7.1.3, "Oracle Database with Oracle RAC One Node" for more information. Provides maximum protection from physical corruptions. Footnote3For qualified one-off patches only. Online Patching allows for dynamic database patching of typical diagnostic patches. Now talking about split-brain concept with respect to oracle . A single standby database architecture consists of the following key traits and recommendations: Standby database resides in Site B. 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 goal of the MAA is to remove the complexity in designing the optimal high availability architecture by providing configuration recommendations and tuning tips to optimize your architecture and Oracle features. With either the active-active or the active-passive category, multiple solutions exist that differ in ease of installation, cost, scalability, and security. 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. Fast-Start Fault Recovery bounds and optimizes instance and database recovery times to minutes. For example, Table 7-1 provides some insight into the probability of different outages during unplanned and planned activities. The problem which could arise out of this situation is that the sane . 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. The data is derived from actual user experiences and from Oracle service requests. 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 . 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. 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. Oracle RAC Split Brain Syndrome Scenerio - Oracle Forums Oracle Data Guard is designed to allow businesses get something useful out of their expensive investment in a disaster-recovery site. Maximum RTO for data corruption, cluster, database, or site failures is in seconds to minutes. Oracle Secure Backup provides a centralized tape backup management solution. In the figure, Node 2 is now the active instance connected to the Oracle database and servicing applications and users. Maximum RTO for instance or node failure is zero for the databaseFootref1. Footnote8With automatic block repair, this should be the most common block corruption repair. The voting result is similar to clusterware voting result. 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. Disaster recovery solutions typically set up two homogeneous sites, one active and one passive. Oracle recommends that you create and store the local backups in the fast recovery area. Flexible and automated high availability solutions ensure that applications you deploy on Oracle Application Server meet the required availability to achieve your business goals. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. . The SELECT statement is used to retrieve information from a database. For high availability, Oracle recommends that you have a minimum of three voting disks. 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. Willing to make additional provisions for remote data protection to protect against database, data, and cluster failures and corruptions. This would lead to collision and corruption of shared data as each sub-cluster assumes ownership of shared data. 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. Each instance is associated with a service: HR, Sales, and Call Center. Oracle RAC Operational Best Practices for the Cloud Created Date: The database consists of a collection of data files, control files, and redo logs located on disk. For physical standby databases, this solution: Supports very high primary database throughput. which node first joined the cluster). Oracle Grid Infrastructure and Oracle RAC make use of Redundant Interconnect Usage that distributes network traffic and ensures optimal communication in the cluster. Oracle Clusterware manages the availability of both the user applications and Oracle databases. The common voting result will be: a. These updates are discarded when the snapshot database is reconverted to a physical standby database. 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 devices convert ESCON or Fibre Channel to the appropriate IP, ATM, or SONET networks. Node 2 is connected to Node 1 and to Oracle Database, but it is currently standby mode. Their strategy further mitigates risk by maintaining multiple standby databases, each implemented using a different architecturesRedo Apply and SQL Apply. 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. These best practices are required to maximize the benefits of each architecture. Although traditional solutions (such as backup and recovery from tape, storage-based remote mirroring, and database log shipping) can deliver some level of high availability, Oracle Data Guard provides the most comprehensive high availability and disaster recovery solution for Oracle databases. Although cold cluster failover is not shown in Figure 7-8, you can configure it by adding a passive node on the secondary site. An Oracle RAC database is connected to three instances on different nodes. So, in a two node situation both the instances will think that the other instance is down because of lack of connection. Network connection changes and other site-specific failover activities may lengthen overall recovery time. 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. Figure 7-1 Single-Node, Nonclustered Oracle Database with an Oracle ASM Instance. When you move the Oracle RAC One Node instance to the newly resized Oracle VM node, you can dynamically increase any limits programmed with Resource Manager Instance Caging. This scenario enables the provider to use existing data centers that are geographically isolated, offering a unique level of high availability. Split Brain: What's new in Oracle Database 12.1.0.2c? Simulate loss of connectivity between two nodes. 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 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. 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. Oracle RAC builds higher levels of availability on top of the standard Oracle Database features. 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. An architecture that combines Oracle Database with Oracle RAC is inherently a highly available system. There is no fancy or expensive hardware required. 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. Footnote2The portion of any application connected to the failed system is temporarily affected. In a "split brain" situation, voting disk is used to determine which node (s) will survive and which node (s) will be evicted. This has the potential for data corruption. When two or more nodes fail to ping or connect to each other via this private interconnect, theclustergets partitionedinto two or more smaller sub-clusters each of which cannot talk to others over the interconnect. Oracle RAC Interview Questions - Coherence and Split-Brain 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 . 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. RAC Split Brain Syndrome. 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. Figure 7-8 shows an Oracle Clusterware and Oracle Data Guard architecture that consists of a primary and a secondary site. Figure 7-3 Oracle Database with Oracle Clusterware (After Cold Cluster Failover). 2. 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. The heartbeat is maintained by background processes like LMON, LMD, LMS and LCK. 1. Oracle RAC - Wikipedia Oracle Data Guard transmits redo data from the primary database to the secondary site to keep the databases synchronized. Footnote2Oracle ASM automatically rebalances stored data when disks are added or removed while the database remains online. Rolling upgrade and patch capabilities for Oracle Clusterware with zero database downtime. Split Brain Syndrome in RAC - I am a DBA Top 25 Oracle RAC Interview Questions and Answers in 2023 Oblivious of the existence of other cluster fragments, each sub-cluster continues to operate independently of the others. Disaster strikes the primary database, and its network connections to both the observer and the target standby database are lost. In a split brain situation, voting disk will be used to determine which node(s) survive and which node(s) will be evicted. Oracle GoldenGate is optimized for replicating data. Both the primary and secondary sites contain Oracle Application Servers, two database instances, and an Oracle database. 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. It allows you to select the table columns depending on a set of criteria. Although using Oracle GoldenGate might require additional work, it offers increased flexibility that might be necessary to meet specific business requirements. 2. Oracle Application Server provides high availability and disaster recovery solutions for maximum protection against any kind of failure with flexible installation, deployment, and security options. For availability reasons, the Oracle database is a single database that is mirrored at both of the sites. 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. Split brain syndrome occurs when the instances in a RAC fails to connect or ping to each other via the private interconnect. Recovery Manager (RMAN) optimizes local repair of data failures. 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. 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. Hi Guru's. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). Fast-start failover is recommended to provide automatic failover without user intervention and bounded recovery time. However, when the data centers are located more than 66 kilometers apart, you must use a series of repeaters and converters from third-party vendors. Oracle Database with Oracle RAC on Extended Clusters. the clusterware identifies the largest sub-cluster, and aborts all the nodes which do. 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. 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. These redundant configurations provide increased availability either through a distributed workload, through a failover setup, or both.
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