This architecture is referred to as an extended cluster. This would lead to collision and corruption of shared data as each sub-cluster assumes ownership of shared data. FAN with integrated Oracle client failover, including Java applications using UCP with Oracle RAC and Oracle Data Guard. In this article I will explore this new feature for one of the possible factors contributing to the node weight, i.e. Oracle Database High Availability Architectures, Choosing the Correct High Availability Architecture, Integrating Application Server High Availability, Integrating High Availability for All Applications. Fast-start failover is recommended to provide automatic failover without user intervention and bounded recovery time. Figure 7-8 shows an Oracle Clusterware and Oracle Data Guard architecture that consists of a primary and a secondary site. . This scenario enables the provider to use existing data centers that are geographically isolated, offering a unique level of high availability. Maximum RTO for instance or node failure is zero for the databaseFootref1. Each instance is associated with a service: HR, Sales, and Call Center. 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. Applications scale in an Oracle RAC environment to meet increasing data processing demands without changing the application code. 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 . The instances monitor each other by checking "heartbeats." A telecommunications provider uses asynchronous redo transport to synchronize a primary database on the West Cost of the United States, with a standby database on the East Coast, over 3,000 miles away. Oracle RAC Operational Best Practices for the Cloud Created Date: 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 Split Brain Syndrome Scenerio. 2. Typically, this is not possible with remote mirroring solutions. 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. In a split brain situation, voting disk will be used to determine which node(s) survive and which node(s) will be evicted. Oracle RAC Split Brain Syndrome Scenerio. 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. You might choose to use Oracle GoldenGate to configure and maintain a logical copy of your production database. Q39) Mention what is split brain syndrome in RAC? Start both the services for database admindb so that serv1 executes on host01 and serv2 executes on host02. Several standby databases in an Oracle RAC environment residing in a cluster of servers, called a grid server. Also, see Figure 5-2 for another example of a multiple standby database environment. 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. Unlike the cold cluster model where one node is completely idle, all instances and nodes can be active to scale your application. 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. Fast Recovery Area manages local recovery-related files. Clusterware will evaluate cluster resources on implied workload 3. . Table 7-5 compares the attainable recovery times of each Oracle high availability architecture for all types of planned downtime. For availability reasons, the Oracle database is a single database that is mirrored at both of the sites. Since I will only explore the scenarios for which functionality has been modified, i.e. Hi Guru's. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). Another possible configuration might be a testing hub consisting of snapshot standby databases. The cold cluster failover solution with Oracle Clusterware provides these additional advantages over a basic database architecture: Automatic recovery of node and instance failures in minutes, Automatic notification and reconnection of Oracle integrated clientsFoot3, Ability to customize the failure detection mechanism. The public and private interconnects, and the Storage Area Network (SAN) are all on separate dedicated channels, with each one configured redundantly. The Maximum Availability Architecture (MAA) is Oracle's best practices blueprint. 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. At the snapshot standby database redo data is received, but it is not applied until the snapshot standby database is reconverted to a physical standby database. Footnote4Database is still available, but a portion of the application connected to the failed system is temporarily affected. The problem which could arise out of this situation is that the sane . The new primary database starts transmitting redo data to the new standby database. For example, if the primary database fails over to one of the standby databases in the Data Guard hub, the new primary database acquires more system and storage resources while the testing resources may be temporarily starved. For example : Footnote6Recovery time for human errors depend primarily on detection time. (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.). From the entry point to an Oracle Application Server system (content cache) to the back-end layer (data sources), all the tiers that are crossed by a request can be configured in a redundant manner with Oracle Application Server. 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. A single standby database architecture consists of the following key traits and recommendations: Standby database resides in Site B. Hence, we observed that when an equal number of database services were running on both nodes, the node with lower node number (host01) survives. Although traditional solutions (such as backup and recovery from tape, storage-based remote mirroring, and database log shipping) can deliver some level of high availability, Oracle Data Guard provides the most comprehensive high availability and disaster recovery solution for Oracle databases. Logical or user failures that manipulate logical data (DMLs and DDLs). The key factors include: Recovery time objective (RTO) and recovery point objective (RPO) for unplanned outages and planned maintenance, Total cost of ownership (TCO) and return on investment (ROI). Data Recovery Advisor diagnoses persistent (on disk) data failures, presents appropriate repair options, and runs repair operations at your request. Also, you can use the Oracle Clusterware ability to relocate applications and application resources (using the crsctl relocate resource command) as a way to move the workload to another node so that you can perform planned system maintenance on the production server. RPO is zero for cluster failover, choice of RPO equal to zero for database failover (Data Guard SYNC), or near-zero (Data Guard ASYNC). Limited support for mixed platforms. 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 . 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. 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. Ina cluster, a private interconnect is used by cluster nodes to monitor each nodes status and communicate with each other. 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. 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. 817202 Mar 1 2016 edited Mar 2 2016. the. More investment and expertise to build and maintain an integrated high availability solution is available. For more information see the MAA white paper "Rapid Oracle RAC One Node Standby Deployment" at. End-users connect to clusters through a public network. 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. Suppose there are 3 nodes in the following situation. All of the business benefits of Oracle RAC and Oracle Data Guard. Maximum RTO for instance or node failure is in seconds to minutes. Oracle High Availability Best Practice recommendations can be found in Oracle Database High Availability Best Practices and in the white papers that can be downloaded from, Table 7-4 Attainable Recovery Times for Unplanned Outages, No downtimeFootref4 if the outage is limited to one building, Hours to days if the outage affects both building. 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. There is no fancy or expensive hardware required. Oracle Automatic Storage Management (Oracle ASM) and Oracle Automatic Storage Management Cluster File System (Oracle ACFS) tolerate storage failures and optimize storage performance and usage. Use a physical standby database if read-only access is sufficient. With Oracle RAC integration, database scalability is possible. Then there are two cohorts: {1, 2} and {3}. Building on top of the local high availability solutions is the Oracle Application Server disaster recovery solution. I go through blogs mentioning what exactly a Split brain syndrome is ( Theoretical Part). 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 figure shows users making local updates to the snapshot standby database. For an Oracle RAC database, each node in a cluster usually has one instance of the running Oracle software that references the database. In an Oracle cluster prior to version 12.1.0.2c, when a split brain problem occurs, the node with lowest node number survives. The Oracle Data Guard broker communicates with the production database, the physical standby database, and the logical standby database. A global manufacturing company used Oracle Data Guard to replace storage-based remote mirroring and maintain a standby database at its recovery site 50 miles away from the primary site. Provides seamless integration with, and migration to, Oracle Real Application Clusters (Oracle RAC) and Oracle Data Guard. All Oracle RAC nodes can be active by implementing multiple Oracle RAC One Node configurations for different databases. Oracle RAC exploits the redundancy that is provided by clustering to deliver availability with n - 1 node failures in an n-node cluster. Oracle Data Guard provides more comprehensive data protection and its more efficient network usage allows plenty of room to grow without the expense of upgrading its network. This is often called the multi-master problem. A highly available and resilient application requires that every component of the application must tolerate failures and changes. Online Patching allows for dynamic database patching of typical diagnostic patches. Different character sets are required between the primary database and its replicas. 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/. (adsbygoogle=window.adsbygoogle||[]).push({}); Split Brain is often used to describe the scenario when two or more nodes in a 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 that the other process(es) are no longer operational or using the said resources. Choice of RPO equal to zero (SYNC) or near-zero (ASYNC). End-users connect to clusters through a public network. 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. Better suited for WANsRemote mirroring solutions based on storage systems often have a distance limitation due to the underlying communication technology (Fibre Channel or ESCON (Enterprise Systems Connection)) used by the storage systems. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. 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. Better resilience and data protectionOracle Data Guard ensures much better data protection and data resilience than remote mirroring solutions. What Is Oracle RAC. Split Brain Syndrome in RAC. What is split brain in Oracle RAC? If the fast recovery area is on the source volume that is remotely mirrored, then you must also remotely mirror the flashback logs. 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. 1. Figure 7-2 shows a configuration that uses Oracle Clusterware to extend the basic Oracle Database architecture and provide cold cluster failover. As the result, 1 or more instance(s) will be evicted.

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