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Rolling upgrade for system, clusterware, operating system, database, and application. 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. 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. 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. 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. Node 1 is connected to Node 2 and to the Oracle database, but Node 1 is currently idle, in standby mode. 817202 Mar 1 2016 edited Mar 2 2016. When the processes of the distributed system rejoin together it is possible that they have conflicting views of system state or resource ownerships. With Oracle Clusterware, . If you configure a single voting disk, then you should use external mirroring to provide redundancy. (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.). Figure 7-7 Oracle Database with Oracle Data Guard on Primary and Multiple Standby Sites, Oracle Data Guard Concepts and Administration for more information about the various types of standby databases and to find out what data types are supported by logical standby databases, Oracle Database High Availability Best Practices for configuration best practices, The "Managing Data Guard Configurations Having Multiple Standby Databases - Best Practices" white paper, and other Oracle Data Guard white papers at. Table 7-2 High Availability Architecture Recommendations. The individual nodes are running fine and can accept user connections and work . Footnote8With automatic block repair, this should be the most common block corruption repair. 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 . The Maximum Availability Architecture (MAA) is Oracle's best practices blueprint. 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. 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. The public and private interconnects, and the Storage Area Network (SAN) are all on separate dedicated channels, with each one configured redundantly. 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. Oracle GoldenGate is optimized for replicating data. Recovery Manager (RMAN) optimizes local repair of data failures. In Oracle RAC each node in the cluster is interconnected through a private interconnect. 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. Oracle Database is a single-instance, standalone (noncluster) database and it is the foundation for all high availability architectures. The voting result is similar to clusterware voting result. Rolling upgrade and patch capabilities for Oracle Clusterware with zero database downtime. In order to make largest number of resources available to the users, the node weight is computed for each node based on number of the resource executing on it and the sub-cluster with higher weight will survive. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. Split Brain Syndrome, In a Oracle RAC environment all the instances/servers communicate with each other using high-speed interconnects on the private network. If the primary system should fail, the first standby database becomes the new primary database. 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. Oracle Clusterware manages the availability of both the user applications and Oracle databases. 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. This is often called the multi-master problem. Unlike the cold cluster model where one node is completely idle, all instances and nodes can be active to scale your application. Longer detection time usually leads to longer recovery time required to repair the appropriate transactions. For more information see the MAA white paper "Rapid Oracle RAC One Node Standby Deployment" at. 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. They will enhance your knowledge and help you to emerge as the best candidate. To ensure data consistency, each instance of a RAC database needs to keep heartbeat with the other instances. The common voting result will be: a. Why is it like that? Database scalability beyond one instance or node. Corruption Prevention, Detection, and Repair detect and prevent some corruptions and lost writes. Table 7-4 shows the recovery time (including detection and client failover time) of an integrated Oracle client, whenever relevant. 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. By using specialized devices, this distance can be extended to 66 kilometers. Maximum RTO for instance or node failure is in seconds to minutes. Nodes 1,2 can talk to each other. Support for heterogeneous platforms, versions, and character sets. The logical standby database may contain additional indexes and materialized views. 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. High availability solution with added data and disaster recovery protection. 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. pagespeed.lazyLoadImages.overrideAttributeFunctions(); Although cold cluster failover is not shown in Figure 7-8, you can configure it by adding a passive node on the secondary site. Online Reorganization and Redefinition allows for dynamic data changes. To provide this transparent failover capability, Oracle Clusterware requires a virtual IP (VIP) address for each node in the cluster. Footnote3The initial investment to build a robust solution is well worth the long-term flexibility and capabilities that Oracle GoldenGate delivers to meet specific business requirements. Applications can easily mask failures to the end user. End-users connect to clusters through a public network. Hi Guru's. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). 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)). For more information about constructing multiple-source replication environments, see the Oracle GoldenGate documentation. New requests are accepted after the Split-Brain event and then performed on potentially corrupted system state (thus potentially corrupting system state even further). There are numerous high availability features that you can use in the Oracle Database single-instance database architecture. host01 is evicted although it has a lower node number. 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. 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. host02 is retained as it has higher number of database services executing. 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. Furthermore, the standby databases can be used for read-only access and subsequently for reader farms, for reporting, and for testing and development. This architecture is the recommended configuration for Maximum Availability Architecture (MAA). The fast-start failover has completed and the target standby database is running in the primary database role. Oracle RAC - Wikipedia 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. For high availability, Oracle recommends that you have a minimum of three voting disks. Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patches. Footnote2The portion of any application connected to the failed system is temporarily affected. Online Application Maintenance and Upgrades with Edition-based redefinition allows an application's database objects to be changed without interrupting the application's availability. In a "split brain" situation, voting disk is used to determine which node (s) will survive and which node (s) will be evicted. Figure 7-7 shows the production database at the primary site and multiple standby databases at secondary sites. This scenario enables the provider to use existing data centers that are geographically isolated, offering a unique level of high availability. Check that only two nodes (host01 and host02) are active and host01 has lower node number, Create two singleton services for the RAC database admindb. Compared to mirroring, Oracle Data Guard provides better performance and is more efficient, Oracle Data Guard always verifies the state of the standby database and validates the data before applying redo data, and Oracle Data Guard enables you to use the standby database for updates while it protects the primary database. For virtualization, Oracle RAC One Node with Oracle VM increases the benefit of Oracle VM with the high availability and scalability of Oracle RAC. When the instance members in a RAC fail to ping/connect to each other via this private network and continue to process data block independently. End-users connect to clusters through a public network. SELECT statements might be as straightforward as selecting a few . 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. 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. the number of database services executing on a node. Disaster recovery solutions typically set up two homogeneous sites, one active and one passive. In addition to maintaining its own disk block, CSSD processes also monitors the disk blocks maintained by the CSSD processes running in other cluster nodes. The clusters that are typical of Oracle RAC environments can provide continuous service for both planned and unplanned outages. This functionality is available starting with Oracle Database 11g Release 2 (11.2.0.2). Split Brain Syndrome Basic Concept in Oracle RAC. All of the business benefits of Oracle RAC and Oracle Data Guard. the number of database services executing on a node. 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. 3. You can have up to 32 voting disks in your cluster. A highly available and resilient application requires that every component of the application must tolerate failures and changes. Footnote6Recovery time for human errors depend primarily on detection time. When the two data centers are located relatively close to each other, extended clusters can provide great protection for some disasters, but not all. Split brain scenario - RAC and PXC. 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. See Section 7.2 for a comparison of the different architectures and highlights of the benefits and considerations. 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. Network & Disk Heartbeats | Oracle Database Internal Mechanism 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. 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 ).

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