Figure 7-9 shows the recommended MAA configuration, with Oracle Database, Oracle RAC, and Oracle Data Guard. These figures show how you can use the Oracle Clusterware framework to make both Oracle Database and your custom applications highly available. Maximum RTO for instance or node failure is in minutes. Figure 7-2 shows a configuration that uses Oracle Clusterware to extend the basic Oracle Database architecture and provide cold cluster failover. 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. Typically, this is not possible with remote mirroring solutions. Split brain scenario - RAC and PXC. All Oracle RAC nodes can be active by implementing multiple Oracle RAC One Node configurations for different databases. It also gives users complete control over the routing of change records from the primary database to a replica database. 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. Footnote1Architectures for which the MO is high might require additional time and expertise to build and maintain, but offer increased flexibility and capabilities required to meet specific business requirements. (See Section 7.1.5 for a complete description.). 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. An Oracle RAC extended cluster is an architecture that provides extremely fast recovery from a site failure and allows for all nodes, at all sites, to actively process transactions as part of single database cluster. For example, for a business that has a corporate campus, the extended Oracle RAC configuration could consist of individual Oracle RAC nodes located in separate buildings. 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. Oracle Clusterware provides tolerance of node failures, whereas Oracle Data Guard provides additional protection against data corruptions, lost writes, and database and site failures. Split Brain Condition occurs when a single cluster has a failure that results in reconfiguration of cluster into multiple partitions, with each partition forming its own sub-cluster without the knowledge of the existence of other. A highly available application must analyze every component that affects the application, including the network topology, application server, application flow and design, systems, and the database configuration and architecture. Suppose there are 3 nodes in the following situation. Oracle Data Guard Advantages Over Traditional Solutions. If it takes seconds to detect a malicious DML or DLL transaction, it typically only requires seconds to flash back the appropriate transactions. 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. 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. Figure 7-6 Primary and Standby Databases and the Observer During Fast-Start Failover. For storage migration, you are required to use both storage arrays by Oracle ASM temporarily. This configuration consists of a central resource supporting 10 applications and databases in the grid, rather than managing 10 separate system or storage units in a nongrid infrastructure. Provides read-only access to synchronized standby database and fast incremental backups to off-load production. 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. the number of database services executing on a node. Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. Fast Recovery Area manages local recover-related files automatically. 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. Figure 7-7 shows the production database at the primary site and multiple standby databases at secondary sites. 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 problem which could arise out of this situation is that the sane . Corruption Prevention, Detection, and Repair detect and prevent some corruptions and lost writes. Fast-start failover is recommended to provide automatic failover without user intervention and bounded recovery time. It is possible, under certain circumstances, to build and deploy an Oracle RAC system where the nodes in the cluster are separated by greater distances. CSSD process in each RAC node maintains a heart beat in a block of size 1 OS block in a specific offset by read/write system calls (pread/pwrite), in the voting disk. 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. Oracle Secure Backup provides a centralized tape backup management solution. In Oracle RAC each node in the cluster is interconnected through a private interconnect. At the time of role transition, more storage and system resources can be allocated toward that application. host01 is retained as it has a lower node number. Oracle Grid Infrastructure and Oracle RAC make use of Redundant Interconnect Usage that distributes network traffic and ensures optimal communication in the cluster. With Oracle RAC integration, database scalability is possible. b. SELECT statements might be as straightforward as selecting a few . We will verify that when an equal number of database services are running on both nodes, the node with lower node number (host01) survives. 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. Oracle RAC exploits the redundancy that is provided by clustering to deliver availability with n - 1 node failures in an n-node cluster. split brain syndrome. Uses a private network and voting disk-based communication to detect and resolve split-brainFoot2 scenarios. However, when you use Oracle Clusterware, there is no need or advantage to using third-party clusterware. Oracle Clusterware: Enables you to use an entire software solution from Oracle, avoiding the cost and complexity of maintaining additional cluster software. Building on top of the local high availability solutions is the Oracle Application Server disaster recovery solution. 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. Traditionally, Oracle RAC is used in a multinode architecture, with many separate database instances running on separate servers. Footnote2Rolling upgrades with Oracle Data Guard incur minimal downtime. In a typical example, the maximum distance between the systems connected in a point-to-point fashion and running synchronously can be only 10 kilometers. If the primary system should fail, the first standby database becomes the new primary database. Footnote8With automatic block repair, this should be the most common block corruption repair. 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 group(cohort) with lower node member survive, in case of same number of node(s) available in each group. Oracle Net Services provide client access to the Application/Web server tier at the top of the figure, Figure 7-4 Oracle Database with Oracle RAC Architecture. High availability benefits and workload balancing outweigh performance concerns. 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. Thus, this feature allows you to consolidate many databases into a single cluster for easier management, while still providing high availability by quickly relocating instances in the event of server failure. Oracle Flashback Technology optimizes logical failure repair. Oracle Data Guard is designed to allow businesses get something useful out of their expensive investment in a disaster-recovery site. The logical standby database may contain additional indexes and materialized views. Footnote1Applications (or a portion of an application) connected to the system that is being maintained may be temporarily affected. Oracle Database with Oracle GoldenGate provides granularity and control over what is replicated and how it is replicated. 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. 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 . It is based on proven Oracle high availability technologies and recommendations. Start both the services for database admindb so that serv1 executes on host01 and serv2 executes on host02. The figure shows the same Oracle Data Guard configuration in three different frames, as described in the following list: The leftmost frame shows the configuration before fast-start failover occurs. See Section 7.2 for a comparison of the different architectures and highlights of the benefits and considerations. 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. High availability solution with added data and disaster recovery protection. The SELECT statement is used to retrieve information from a database. Node 2 is connected to Node 1 and to Oracle Database, but it is currently standby mode. Common messages in instance alert log are similar to: In above example, instance 2 LMD0 (pid 29940) is the receiver in IPC Send timeout. which node first joined the cluster). Recovery Manager (RMAN) optimizes local repair of data failures. Then there are two cohorts: {1, 2} and {3}. Footnote1Rolling upgrades with Oracle Clusterware and Oracle RAC incur zero downtime. 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 . You can define multiple application VIPs, with generally one application VIP defined for each application running. 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. Figure 7-9 Oracle Database with Oracle RAC and Oracle Data Guard - MAA. For more information, see Oracle Data Guard Concepts and Administration or the Oracle Streams Replication Administrator's Guide. Oracle RAC builds higher levels of availability on top of the standard Oracle Database features. 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 . 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. Flexible and automated high availability solutions ensure that applications you deploy on Oracle Application Server meet the required availability to achieve your business goals. 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. Maximum RTO for instance or node failure is in seconds. Zero downtime when using the provisioning capability in Oracle Enterprise Manager Grid Control.

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