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 . 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. 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. 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. Split Brain Resolution in Oracle Clusterware 12c Rel 2 1. 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. Any database in a Data Guard configuration, whether a primary or standby database, can be an Oracle RAC One Node database. High availability benefits and workload balancing outweigh performance concerns. 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. 3. 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. The center frame shows the configuration during fast-start failover. Provides the simplicity of a physical replica. Note, however, that the synchronous redo transport does not impose any physical distance limitation. the. It allows you to select the table columns depending on a set of criteria. The script content on this page is for navigation purposes only and does not alter the content in any way. 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. 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. 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. Oracle Application Server provides redundancy by offering support for multiple instances supporting the same workload. 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. It is based on proven Oracle high availability technologies and recommendations. Furthermore, operational practices across role transitions are simplified when the sites are symmetric. Footnote8With automatic block repair, this should be the most common block corruption repair. Figure 7-8 shows an Oracle Clusterware and Oracle Data Guard architecture that consists of a primary and a secondary site. What Is Oracle RAC. (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 Flashback Technology optimizes logical failure repair. The figure shows Oracle Database with Oracle Data Guard architecture. Willing to make additional provisions for remote data protection to protect against database, data, and cluster failures and corruptions. Traditionally, Oracle RAC is used in a multinode architecture, with many separate database instances running on separate servers. Figure 7-2 shows a configuration that uses Oracle Clusterware to extend the basic Oracle Database architecture and provide cold cluster failover. Off-load read-only, reporting, testing and backup activities to the standby database. For an Oracle RAC database, each node in a cluster usually has one instance of the running Oracle software that references the database. Suppose there are 3 nodes in the following situation. Hi Guru's. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). 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. Nodes 1,2 can talk to each other. 2. High availability functionality to manage third-party applications, Rolling release upgrades of Oracle Clusterware. 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. The Oracle Application Server High Availability Guide describes the following high availability services in Oracle Application Server in detail: Process death detection and automatic restart. 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. Footnote4Tables can be reorganized online using the DBMS_REDEFINITION package. (adsbygoogle=window.adsbygoogle||[]).push({}); The biggest risk following a Split-Brain event is the potential for corrupting system state. Figure 7-9 shows the recommended MAA configuration, with Oracle Database, Oracle RAC, and Oracle Data Guard. The following list describes examples of Oracle Data Guard configurations using single standby databases: A national energy company uses a standby database located in a separate facility 10 miles away from its primary data center. 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. the number of database services executing on a node. Oracle RAC builds higher levels of availability on top of the standard Oracle Database features. 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. To provide this transparent failover capability, Oracle Clusterware requires a virtual IP (VIP) address for each node in the cluster. The rightmost frame shows the configuration after fast-start failover has occurred. Figure 7-9 Oracle Database with Oracle RAC and Oracle Data Guard - MAA. 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. Node 1 is connected to Node 2 and to the Oracle database, but Node 1 is currently idle, in standby mode. It also gives users complete control over the routing of change records from the primary database to a replica database. Any of these processes experience IPC Send time out will incur communication reconfiguration and instance eviction to avoid split brain. 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 High Availability Best Practice recommendations can be found in Oracle Database High Availability Best Practices and in the white papers that can be downloaded from, Table 7-4 Attainable Recovery Times for Unplanned Outages, No downtimeFootref4 if the outage is limited to one building, Hours to days if the outage affects both building. Oracle RAC Split Brain Syndrome Scenerio. The heartbeat is maintained by background processes like LMON, LMD, LMS and LCK. Why is it like that? split brain syndrome. 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. A single standby database architecture consists of the following key traits and recommendations: Standby database resides in Site B. 1. Clients are connected to the logical standby database and can work with its data. 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). To ensure data consistency, each instance of a RAC database needs to keep heartbeat with the other instances. Common messages in instance alert log are similar to: In above example, instance 2 LMD0 (pid 29940) is the receiver in IPC Send timeout. In this article I will explore this new feature for one of the possible factors contributing to the node weight, i.e. The data is derived from actual user experiences and from Oracle service requests. Online Application Maintenance and Upgrades with Edition-based redefinition allows an application's database objects to be changed without interrupting the application's availability. This architecture is referred to as an extended cluster. The production database transmits redo data (either synchronously or asynchronously) to redo log files at the physical standby database. 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. To simulate loss of connectivity between two nodes, stop the private network service on one of the nodes: Verify that host01 is retained as it has a lower node number and host02 is evicted: To simulate loss of connectivity between two nodes, stop private network service on one of the nodes: Verify that host02 is retained as it has higher number of database services executing and host01 is evicted although it has a lower node number: If the sub-clusters are of the different sizes, the functionality is same as earlier, i.e. Footnote3Recovery time consists largely of the time it takes to restore the failed system. Oracle Restart enhances the availability of Oracle databases, listeners, and Oracle ASM instances in a single-instance environment by monitoring and automatically restarting Oracle processes. Oracle GoldenGate is optimized for replicating data. The active site is generally called the production site, and the passive site is called the standby site. Better resilience and data protectionOracle Data Guard ensures much better data protection and data resilience than remote mirroring solutions. The new primary database starts transmitting redo data to the new standby database. RAC Split Brain Syndrome. 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. Name of the cluster: Cluster01.example.com, Number of nodes: 3 (host01, host02, host03), Instances of RAC database: admindb1 on host01. 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. Flexible and automated high availability solutions ensure that applications you deploy on Oracle Application Server meet the required availability to achieve your business goals.
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