Fast-start failover is recommended to provide automatic failover without user intervention and bounded recovery time. Oracle Application Server instances can be installed in either site as long as they do not interfere with the instances in the disaster recovery setup. Willing to make additional provisions for remote data protection to protect against database, data, and cluster failures and corruptions. Suppose there are 3 nodes in the following situation. The database consists of a collection of data files, control files, and redo logs located on disk. This architecture is referred to as an extended cluster. It requires only a standard TCP/IP-based network link between the two computers. These figures show how you can use the Oracle Clusterware framework to make both Oracle Database and your custom applications highly available. Each instance is associated with a service: HR, Sales, and Call Center. The figure shows users making local updates to the snapshot standby database. Section 7.1.8 describes how you can achieve the highest level of availability with Oracle RAC and Oracle Data Guard. When two or more nodes fail to ping or connect to each other via this private interconnect, theclustergets partitionedinto two or more smaller sub-clusters each of which cannot talk to others over the interconnect. Oracle RAC Split Brain Syndrome Scenerio - Oracle Forums When the two data centers are located relatively close to each other, extended clusters can provide great protection for some disasters, but not all. 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 ). Thus, we observed that when unequal number of database services are running on the two nodes, the node with higher number of database services survives even though it has a higher node number. Limited support for mixed platforms. 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. After you have chosen an architecture, then implement it using the operational and configuration best practices described in the MAA white papers and in Oracle Database High Availability Best Practices. Figure 7-6 shows the relationships between the primary database, target standby database, and the observer before, during, and after a fast-start failover. Rolling upgrade for system, clusterware, operating system, database, and application. Table 7-2 High Availability Architecture Recommendations. Oracle GoldenGate can capture changes at a source database, and the captured changes can be propagated asynchronously to replica databases. With Oracle Clusterware, you can provide a cold cluster failover to protect an Oracle Database instance from a system or server failure. RAC Split Brain Syndrome. 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. The configuration can be an active-active configuration using Oracle Application Server Cluster or an active-passive configuration using Oracle Application Server Cold Cluster Failover. Figure 7-2 shows a configuration that uses Oracle Clusterware to extend the basic Oracle Database architecture and provide cold cluster failover. Q39) Mention what is split brain syndrome in RAC? 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. The application VIP is tied to the application by making it dependent on the application resource defined by Cluster Ready Services (CRS). We will verify that when an equal number of database services are running on both nodes, the node with lower node number (host01) survives. In a non-RAC Oracle database, a single instance accesses a single database. 008 - How Node Membership Happens in RAC? - What is Voting Disk & Split 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. Oracle RAC One Node provides relocation of Oracle RAC primary and standby databases configured with Oracle Data Guard (This functionality is available starting with Oracle Database 11g Release 2 (11.2.0.2)). Oracle Data Guard transmits redo data from the primary database to the secondary site to keep the databases synchronized. Oracle Data Guard is a high availability and disaster-recovery solution that provides very fast automatic failover (referred to as fast-start failover) in database failures, node failures, corruption, and media failures. 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. End-users connect to clusters through a public network. Higher ROIBusinesses must obtain maximum value from their IT investments, and ensure that no IT infrastructure is sitting idle. Footnote6Recovery time for human errors depend primarily on detection time. Footnote1Recovery time indicated applies to database and existing connection failover. If zero data loss is required with minimum performance impact on the primary database, then the best practice is to locate the secondary site within 200 miles of the primary database. 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 . The system resources can be dynamically allocated and deallocated depending on various priorities. Provides read-only access to synchronized standby database and fast incremental backups to off-load production. 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. 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. 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. This scenario enables the provider to use existing data centers that are geographically isolated, offering a unique level of high availability. Online Reorganization and Redefinition allows for dynamic data changes. Oracle Database with Oracle GoldenGate provides granularity and control over what is replicated and how it is replicated. Support is for single-instance databases only. Oracle RAC - Wikipedia Footnote4Tables can be reorganized online using the DBMS_REDEFINITION package. Upon detecting the break in communication, the observer attempts to reestablish a connection with the primary database for the amount of time defined by the FastStartFailoverThreshold property before initiating a fast-start failover. Simulate loss of connectivity between two nodes. Name of the cluster: Cluster01.example.com, Number of nodes: 3 (host01, host02, host03), Instances of RAC database: admindb1 on host01. In simple terms "Split brain" means that there are 2 or more distinct sets of nodes, or "cohorts", with no communication between the two cohorts. b. 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. 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. Oracle Database High Availability Best Practices for information about configuring Oracle Database 11g with Oracle RAC on extended clusters, White papers about extended (stretch) clusters and about using standard NFS to support a third voting disk on an extended cluster configuration at http://www.oracle.com/technetwork/database/clustering/overview/. Oblivious of the existence of other cluster fragments, each sub-cluster continues to operate independently of the others. Furthermore, the standby databases can be used for read-only access and subsequently for reader farms, for reporting, and for testing and development. 1. Traditionally, Oracle RAC is used in a multinode architecture, with many separate database instances running on separate servers. In Oracle RAC, all the instances/servers communicate with each other using a private network. 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 . Typically, this is not possible with remote mirroring solutions. Any database in a Data Guard configuration, whether a primary or standby database, can be an Oracle One Node database. pagespeed.lazyLoadImages.overrideAttributeFunctions(); Table 7-2 recommends architectures based on your business requirements for RTO, RPO, MO, scalability, and other factors. Suppose there are 3 nodes in the following situation. All single-instance high availability features, such as the Flashback technologies and online reorganization, also apply to Oracle RAC. The goal of the MAA is to remove the complexity in designing the optimal high availability architecture by providing configuration recommendations and tuning tips to optimize your architecture and Oracle features. In previous releases, technologies like bonding or trunking were used to make use of redundant networks for the interconnect. 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". 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.
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