For storage migration, you are required to use both storage arrays by Oracle ASM temporarily. Figure 7-6 Primary and Standby Databases and the Observer During Fast-Start Failover. The database consists of a collection of data files, control files, and redo logs located on disk. 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. Although both types of solutions provide high availability, active-active solutions generally offer higher scalability and faster failover, although they tend to be more expensive. 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. If it takes seconds to detect a malicious DML or DLL transaction, it typically only requires seconds to flash back the appropriate transactions. Start both the services for database admindb so that equal number of database services execute on both the nodes. These devices convert ESCON or Fibre Channel to the appropriate IP, ATM, or SONET networks. Node Weighting for Split Brain Resolution Without better understanding of what is critical or of higher priority to the customer's workload, Oracle Clusterware has always resolved split brain conditions in favor of the cluster cohort containing the node with the lowest node number (i.e. Dynamic Resource Provisioning allows for dynamic system changes. Database scalability beyond one instance or node. Controlfile is used similarly to voting disk in clusterware layer to determine which instance(s) survive and which instance(s) evict. Start both the services for database admindb so that serv1 executes on host01 and serv2 executes on host02. Corruption Prevention, Detection, and Repair detect and prevent some corruptions and lost writes. Higher ROIBusinesses must obtain maximum value from their IT investments, and ensure that no IT infrastructure is sitting idle. It allows you to select the table columns depending on a set of criteria. It is based on proven Oracle high availability technologies and recommendations. (adsbygoogle=window.adsbygoogle||[]).push({}); The biggest risk following a Split-Brain event is the potential for corrupting system state. For more information, see Oracle Data Guard Concepts and Administration or the Oracle Streams Replication Administrator's Guide. 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. These figures show how you can use the Oracle Clusterware framework to make both Oracle Database and your custom applications highly available. 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. When the two data centers are located relatively close to each other, extended clusters can provide great protection for some disasters, but not all. These best practices are required to maximize the benefits of each architecture. For more information see the MAA white paper "Rapid Oracle RAC One Node Standby Deployment" at. If you configure a single voting disk, then you should use external mirroring to provide redundancy. As the result, 1 or more instance(s) will be evicted. It also gives users complete control over the routing of change records from the primary database to a replica database. In previous releases, technologies like bonding or trunking were used to make use of redundant networks for the interconnect. c. Some improvement has been made to ensure node(s) with lower load survive in case the eviction is caused by high system load. For availability reasons, the Oracle database is a single database that is mirrored at both of the sites. Oracle Clusterware cold cluster failover combined with Oracle Data Guard makes a tightly integrated solution in which failover to the secondary node in the cold cluster failover is transparent and does not require you to reconfigure the Oracle Data Guard environment or perform additional steps. The system resources can be dynamically allocated and deallocated depending on various priorities. It also allows the storage to be laid out in a different fashion from the primary computer. For more information about constructing multiple-source replication environments, see the Oracle GoldenGate documentation. Oracle GoldenGate can capture changes at a source database, and the captured changes can be propagated asynchronously to replica databases. 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. Then there are two cohorts: {1, 2} and {3}. Another possible configuration might be a testing hub consisting of snapshot standby databases. 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 ). The term "Split-Brain" is often used to describe the scenario when two or more co-operating processes in a distributed system, typically a high availability 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 . 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 problem which could arise out of this situation is that the sane . Oracle Enterprise Manager support for patch application simplifies software maintenance. These redundant configurations provide increased availability either through a distributed workload, through a failover setup, or both. 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. We will verify that when an unequal number of database services are running on the two nodes, the node hosting the higher number of database services survives even if it has a higher node number. Footnote6Recovery time for human errors depend primarily on detection time. Oracle Flashback Technology optimizes logical failure repair. When a database is started, Oracle Database allocates a memory area called the System Global Area (SGA) and starts one or more Oracle Database processes. 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. 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. The heartbeat is maintained by background processes like LMON, LMD, LMS and LCK. 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. 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. Each instance is associated with a service: HR, Sales, and Call Center. 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. 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. In such a scenario, integrity of the cluster and its data might be compromised due to uncoordinated writes to shared data by independently operating nodes. The data is derived from actual user experiences and from Oracle service requests. Each site is a self-contained system. See Section 7.1.3, "Oracle Database with Oracle RAC One Node" for more information. Maximum RTO for instance or node failure is zero for the databaseFootref1. It requires only a standard TCP/IP-based network link between the two computers. the number of database services executing on a node. Furthermore, the standby databases can be used for read-only access and subsequently for reader farms, for reporting, and for testing and development. Traditionally, Oracle RAC is used in a multinode architecture, with many separate database instances running on separate servers. By using specialized devices, this distance can be extended to 66 kilometers. As a result, equal number of database services execute on both the nodes. Zero downtime when using the provisioning capability in Oracle Enterprise Manager Grid Control. To provide this transparent failover capability, Oracle Clusterware requires a virtual IP (VIP) address for each node in the cluster. You can allocate server resources to multiple instances using Oracle Database Resource Manager Instance Caging. 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. This has the potential for data corruption. Common messages in instance alert log are similar to: In above example, instance 2 LMD0 (pid 29940) is the receiver in IPC Send timeout. 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. Then, the redo data is applied from the logs to the physical standby database, which backs up the redo data to physical media. So, in a two node situation both the instances will think that the other instance is down because of lack of connection. Figure 7-1 Single-Node, Nonclustered Oracle Database with an Oracle ASM Instance. Commonly, one will see messages similar to the followings in ocssd.log when split brain happens: Above messages indicate the communication from node 2 to node 1 is not working, hence node 2 only sees 1 node, but node 1 is working fine and it can see two nodes in the cluster. 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. Any database in a Data Guard configuration, whether a primary or standby database, can be an Oracle RAC One Node database. 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. They will enhance your knowledge and help you to emerge as the best candidate. Footnote3Recovery time consists largely of the time it takes to restore the failed system. The group(cohort) with more cluster nodes survive 3. You can configure the failed application connections to fail over to the replica. For physical standby databases, this solution: Supports very high primary database throughput. Node 2 is connected to Node 1 and to Oracle Database, but it is currently standby mode. Oracle RAC One Node allows you to run one instance of an Oracle RAC database on a single node in a cluster. 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. split brain syndrome. 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". The voting result is similar to clusterware voting result. Oracle Application Server provides redundancy by offering support for multiple instances supporting the same workload. Online Patching allows for dynamic database patching of typical diagnostic patches.

Remington Model 760 Gamemaster, Articles W