The individual nodes are running fine and can accept user connections and work . The application VIP is tied to the application by making it dependent on the application resource defined by Cluster Ready Services (CRS). 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. the clusterware identifies the largest sub-cluster, and aborts all the nodes which do. Oracle GoldenGate can capture changes at a source database, and the captured changes can be propagated asynchronously to replica databases. Online Application Maintenance and Upgrades with Edition-based redefinition allows an application's database objects to be changed without interrupting the application's availability. Although cold cluster failover is not shown in Figure 7-8, you can configure it by adding a passive node on the secondary site. Oracle Data Guard Advantages Over Traditional Solutions. Table 7-3 identifies the additional capabilities provided by the architectures that build on Oracle Database and attempts to label each architecture with its greatest strengths. Unlike the cold cluster model where one node is completely idle, all instances and nodes can be active to scale your application. Footnote3Recovery time consists largely of the time it takes to restore the failed system. Vijay.Cherukuri-Oracle Dec 18 2011 edited Nov 5 2012. Oracle RAC on an extended cluster provides greater availability than a local Oracle RAC cluster, but an extended cluster may not completely fulfill the disaster recovery requirements of your organization . Oracle RAC Split Brain Syndrome Scenerio. A highly available and resilient application requires that every component of the application must tolerate failures and changes. Both the primary and secondary sites contain Oracle Application Servers, two database instances, and an Oracle database. This architecture is identical to the single-standby database architecture that was described in Section 7.1.5.1, except that there are multiple standby databases in the same Oracle Data Guard configuration. With the Oracle Grid technologies, you can enable a high level of usage and low TCO without sacrificing business requirements. Section 3.4.1 describes how Oracle Clusterware is software that, when installed on servers running the same operating system, enables the servers to be bound together to operate as if they are one server, and manages the availability of user applications and Oracle databases. Off-load read-only, reporting, testing and backup activities to the standby database. 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. Fast Recovery Area manages local recover-related files automatically. Similar to using Oracle Data Guard in SQL Apply mode, Oracle GoldenGate can capture database changes, propagate them to destinations, and apply the changes at these destinations. 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. Online Application Maintenance and Upgrades with Edition-based redefinition allows an application's database objects to be changed without interrupting the application's availability, Automatic and fast failover for computer failure, Minimum rolling upgrade capabilities for system, clusterware, and operating systemFootref1, High availability, scalability, and foundation of server database grids, Automatic recovery of failed nodes and instances, Fast application notification (FAN) with integrated Oracle client failover, FAN with integrated Oracle client failover for pooled resources and third-party vendor middle tiers. Disaster recovery solutions typically set up two homogeneous sites, one active and one passive. 2. If the fast recovery area is on the source volume that is remotely mirrored, then you must also remotely mirror the flashback logs. For more information see the MAA white paper "Rapid Oracle RAC One Node Standby Deployment" at. Split Brain Resolution in Oracle Clusterware 12c Rel 2 1. 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. A nationally recognized insurance provider in the U.S. maintains two standby databases in the same Oracle Data Guard configuration: one physical standby and one logical standby database. Figure 7-6 shows the relationships between the primary database, target standby database, and the observer before, during, and after a fast-start failover. Provides maximum protection from physical corruptions. Footnote5Storage failures are prevented by using Oracle ASM with mirroring and its automatic rebalance capability. Footnote8With automatic block repair, this should be the most common block corruption repair. Nodes 1,2 can talk to each other. You should determine if both sites are likely to be affected by the same disaster. 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. Figure 7-9 Oracle Database with Oracle RAC and Oracle Data Guard - MAA. Oracle Clusterware provides a number of benefits over third-party clusterware. All Oracle RAC nodes can be active by implementing multiple Oracle RAC One Node configurations for different databases. 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. In Oracle RAC, all the instances/servers communicate with each other using a private network. 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). the number of database services executing on a node. 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. Each instance is associated with a service: HR, Sales, and Call Center. 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. Maximum RTO for instance or node failure is zero for the databaseFootref1. This section contains the following topics: Oracle Application Server High Availability Architectures, High Availability Services in Oracle Application Server. Then there are two cohorts: {1, 2} and {3}. host02 is retained as it has higher number of database services executing. So, in a two node situation both the instances will think that the other instance is down because of lack of connection. Furthermore, the standby databases can be used for read-only access and subsequently for reader farms, for reporting, and for testing and development. The instances monitor each other by checking "heartbeats." The observer (thin client watchdog) resides in the application tier and monitors the availability of the primary database. Footnote2Oracle ASM automatically rebalances stored data when disks are added or removed while the database remains online. Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patches. Footnote1Recovery time indicated applies to database and existing connection failover. Choice of RPO equal to zero (SYNC) or near-zero (ASYNC). 817202 Mar 1 2016 edited Mar 2 2016. Typically, this is not possible with remote mirroring solutions. Site configurations are on heterogeneous platforms. The figure shows Oracle Database with Oracle Data Guard architecture. With the snapshot standby database hub, you can use the combined storage and server resources of a grid instead of building and managing individual servers for each application. Support for fine-grained, n-way multimaster, hub-and-spoke, or many-to-one replication architectures. In a split brain situation, voting disk is used to determine which node(s) will survive and which node(s) will be evicted. Disaster strikes the primary database, and its network connections to both the observer and the target standby database are lost. 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. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. 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. Any database in a Data Guard configuration, whether a primary or standby database, can be an Oracle RAC One Node database. Online Patching allows for dynamic database patches for diagnostic and interim patches. You should adopt the MAA best practices to achieve the optimal recovery time and configuration. If all the sub-clusters are of the same size, the sub-cluster having the lowest numbered node survives so that, in a 2-node cluster, the node with the lowest node number will survive. Split Brain: Whats new in Oracle Database 12.1.0.2c? Footnote1Rolling upgrades with Oracle Clusterware and Oracle RAC incur zero downtime. End-users connect to clusters through a public network. This scenario enables the provider to use existing data centers that are geographically isolated, offering a unique level of high availability. 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. See Section 7.2 for a comparison of the different architectures and highlights of the benefits and considerations. Any database in a Data Guard configuration, whether a primary or standby database, can be an Oracle One Node database. Oracle Database with Oracle GoldenGate provides granularity and control over what is replicated and how it is replicated. This book focuses primarily on the database high availability solutions. Oracle RAC exploits the redundancy that is provided by clustering to deliver availability with n - 1 node failures in an n-node cluster. 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. Footnote3For qualified one-off patches only. 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. The servers on which you want to run Oracle Clusterware must be running the same operating system. An architecture that combines Oracle Database with Oracle RAC is inherently a highly available system. You can configure Oracle GoldenGate with Oracle Data Guard to provide protection for the individual databases in the configuration. 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. Flexible and automated high availability solutions ensure that applications you deploy on Oracle Application Server meet the required availability to achieve your business goals. Each site is a self-contained system. RAC Split Brain Syndrome. They will enhance your knowledge and help you to emerge as the best candidate. Uses a private network and voting disk-based communication to detect and resolve split-brainFoot2 scenarios. 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. Name of the cluster: Cluster01.example.com, Number of nodes: 3 (host01, host02, host03), Instances of RAC database: admindb1 on host01. Online Reorganization and Redefinition allows for dynamic data changes. By using specialized devices, this distance can be extended to 66 kilometers. Footnote4Tables can be reorganized online using the DBMS_REDEFINITION package. Footnote2The portion of any application connected to the failed system is temporarily affected. 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. Recovery Manager optimizes local repair of data failures using local backups. Starting in Oracle Database 12.1.0.2c, the new algorithm to determine the node(s) to be retained / evicted is as follows: Now I will demonstrate this new feature in an Oracle 12.1.0.2c standard 3 node cluster, using an RAC database called admindb for one of the possible factors contributing to the node weight, i.e. Customer can designate which server(s) and resource(s) are critical 2. 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 . Figure 7-2 shows a configuration that uses Oracle Clusterware to extend the basic Oracle Database architecture and provide cold cluster failover. 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. Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. The Maximum Availability Architecture (MAA) is Oracle's best practices blueprint. Maximum RTO for instance or node failure is in seconds. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. Figure 7-6 Primary and Standby Databases and the Observer During Fast-Start Failover.
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