Fast-start failover is recommended to provide automatic failover without user intervention and bounded recovery time. An exception is undropping a table, which is literally instantaneous regardless of detection time. If the sub-clusters are of the different sizes, the clusterware identifies the largest sub-cluster, and aborts all the nodes which do. You can allocate server resources to multiple instances using Oracle Database Resource Manager Instance Caging. New requests are accepted after the Split-Brain event and then performed on potentially corrupted system state (thus potentially corrupting system state even further). The heartbeat is maintained by background processes like LMON, LMD, LMS and LCK. (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. All of the business benefits of Oracle RAC. 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. Oracle Enterprise Management support for Oracle ASM and Oracle ACFS, Grid Plug and Play, Cluster Resource Management, Oracle Clusterware and Oracle RAC Provisioning and patching, Figure 7-4 shows Oracle Database with Oracle RAC architecture. Figure 7-3 Oracle Database with Oracle Clusterware (After Cold Cluster Failover). 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. 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. 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. Nodes 1,2 can talk to each other. In Oracle Database 11g Release 2 (11.2), Oracle RAC One Node or Oracle RAC is the preferred solution over Oracle Clusterware (Cold Cluster Failover) because it is a more complete and feature-rich solution. 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. Oracle RAC builds higher levels of availability on top of the standard Oracle Database features. Then there are two cohorts: {1, 2} and {3}. Oracle Quality of Service (QoS) Management for policy-based run-time management of resource allocation to database workloads to ensure service levels are met in order of business need under dynamic conditions. The sum of benefits of Oracle Clusterware with Oracle Data Guard, Best high availability, data protection, and disaster-recovery solution with scalability built in, The sum of benefits of Oracle RAC with Oracle Data Guard, Oracle Database with Oracle GoldenGateFoot3, Bidirectional replication and information management, Replica database (or databases) available for read/write use, Fast failover for computer failure and storage failure, Minimum downtime for computer or site maintenance and database and application upgrades. Suppose there are 3 nodes in the following situation. 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. 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. End-users connect to clusters through a public network. There are three typical causes of corruption: 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. In Oracle RAC each node in the cluster is interconnected through a private interconnect. 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. 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. 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 an Oracle RAC database, each node in a cluster usually has one instance of the running Oracle software that references the database. The data is derived from actual user experiences and from Oracle service requests. Also, see Figure 5-2 for another example of a multiple standby database environment. As a result, equal number of database services execute on both the nodes. 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. 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. Oracle Grid Infrastructure and Oracle RAC make use of Redundant Interconnect Usage that distributes network traffic and ensures optimal communication in the cluster. Then this process is referred as Split Brain Syndrome. FAN with integrated Oracle client failover, including Java applications using UCP with Oracle RAC and Oracle Data Guard. The operation of an Oracle Clusterware cold cluster failover is depicted in Figure 7-2 and Figure 7-3. If all the sub-clusters are of the same size, the sub-cluster having the lowest numbered node survives so that, in a 2-node cluster, the node with the lowest node number will survive. The logical standby database may contain additional indexes and materialized views. Oracle recommends that you use automatic undo management with sufficient space to attain your desired undo retention guarantee, enable Oracle Flashback Database, and allocate sufficient space and I/O bandwidth in the fast recovery area. Includes all of the features required for cluster management, including node membership, group services, global resource management, and high availability functions such as managing third-party applications, event management, and Oracle notification services that enable Oracle clients to reconnect to the new primary database after a failure. Customer can designate which server(s) and resource(s) are critical 2. The basic function of a cold cluster failover is to monitor a database instance running on a server, and if a failure is detected, to restart the instance on a spare server in the cluster. Corruption Prevention, Detection, and Repair detect and prevent some corruptions and lost writes. During normal operation, the production site services requests; in the event of a site failover or switchover, the standby site takes over the production role and all requests are routed to that site. What is split brain in Oracle RAC? Footnote7Recovery time depends on block media recovery and the time it takes to restore a consistent block from the flashback logs or database backups, and to recover the block by applying all the redo from archive logs and online redo logs. 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. Q39) Mention what is split brain syndrome in RAC? Clusterware will evaluate cluster resources on implied workload 3. . The servers on which you want to run Oracle Clusterware must be running the same operating system. 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. A highly available and resilient application requires that every component of the application must tolerate failures and changes. RAC Split Brain Syndrome. Better resilience and data protectionOracle Data Guard ensures much better data protection and data resilience than remote mirroring solutions. Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patches. You might choose to use Oracle GoldenGate to configure and maintain a logical copy of your production database. Similar to using Oracle Data Guard in SQL Apply mode, Oracle GoldenGate can capture database changes, propagate them to destinations, and apply the changes at these destinations. 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. Name of the cluster: Cluster01.example.com, Number of nodes: 3 (host01, host02, host03), Instances of RAC database: admindb1 on host01. 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. By reducing the combinations of software that you must coordinate and support, you can increase the manageability and availability of your system software. (adsbygoogle=window.adsbygoogle||[]).push({}); The biggest risk following a Split-Brain event is the potential for corrupting system state. Footnote6Recovery time for human errors depend primarily on detection time. This chapter describes the various high availability architectures in an Oracle environment and helps you to choose the correct architecture for your organization. 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. Footnote4Tables can be reorganized online using the DBMS_REDEFINITION package. Provides read-only access to synchronized standby database and fast incremental backups to off-load production. Flexible propagation and management of data, transactions, and events. However, when you use Oracle Clusterware, there is no need or advantage to using third-party clusterware. Following the execution of a SELECT statement, a tabular result is held in a result table (called a result set). The premise of the Data Guard hub is that it provides higher utilization with lower cost. Figure 7-8 Oracle Clusterware (Cold Cluster Failover) and Oracle Data Guard, The application servers on the secondary site are connected to the WAN traffic manager by a dotted line to indicate that they are not actively processing client requests at this time. Please enroll for the Oracle DBA Interview Question Course.https://learnomate.org/courses/oracle-dba-interview-question/Use DBA50 to get 50% discountPlease s. Oracle Clusterware provides a number of benefits over third-party clusterware. host02 is retained as it has higher number of database services executing. Split Brain Syndrome Basic Concept in Oracle RAC. 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 scenario - RAC and PXC. A logical copy configured and maintained using Oracle GoldenGate is called a replica, not a logical standby database, because it provides many capabilities that are beyond the scope of the normal definition of a standby database. Unlike a traditional monolithic database server that is expensive and is not flexible to changing capacity and resource demands, Oracle RAC combines the processing power of multiple interconnected computers to provide system redundancy, scalability, and high availability. In Oracle RAC, all the instances/servers communicate with each other using a private network. Both the primary and secondary sites contain Oracle Application Servers, two database instances, and an Oracle database. Oracle Data Guard is designed so that it does not affect the Oracle database writer (DBWR) process that writes to data files, because anything that slows down the DBWR process affects database performance. This book focuses primarily on the database high availability solutions. You can achieve the highest level of availability when using Oracle RAC and Oracle Data Guard and there is no need to make application changes to use these Oracle Database features. (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.). This is called Split Brain. host01 is evicted although it has a lower node number. Oracle recommends that you use the following Oracle features to make a standalone database on a single computer available for certain failures and planned maintenance activities: Fast-Start Fault Recovery bounds and optimizes instance and database recovery times. For example, you can put the files on different disks, volumes, file systems, and so on. For availability reasons, the Oracle database is a single database that is mirrored at both of the sites. This functionality is available starting with Oracle Database 11g Release 2 (11.2.0.2). Node 2 is connected to Node 1 and to Oracle Database, but it is currently standby mode. However, remote mirroring solutions affect DBWR process performance because they subject all DBWR process write I/O's to network and disk I/O induced delays inherent to synchronous, zero-data-loss configurations. 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. Start both the services for database admindb so that serv1 executes on host01 and serv2 executes on host02. Support for heterogeneous platforms, versions, and character sets. 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. When the processes of the distributed system rejoin together it is possible that they have conflicting views of system state or resource ownerships. Footnote3For qualified one-off patches only. The following list summarizes the advantages of using Oracle Data Guard compared to using remote mirroring solutions: Better network efficiencyWith Oracle Data Guard, only the redo data needs to be sent to the remote site and the redo data can be compressed to provide even greater network efficiency. Oracle recommends that you create and store the local backups in the fast recovery area. It also allows the storage to be laid out in a different fashion from the primary computer. The production database transmits redo data (either synchronously or asynchronously) to redo log files at the physical standby database. For more information about constructing multiple-source replication environments, see the Oracle GoldenGate documentation. In Oracle RAC each node in the cluster is interconnected through a private interconnect. The voting result is similar to clusterware voting result. For more information see the MAA white paper "Rapid Oracle RAC One Node Standby Deployment" at. 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. Oracle Data Guard Advantages Compared to Remote Mirroring Solutions. (See Section 7.1.5 for a complete description.). 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. You can configure the failed application connections to fail over to the replica. Each site is a self-contained system. The observer (thin client watchdog) resides in the application tier and monitors the availability of the primary database. 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. 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. 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 . 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. 1. Building on top of the local high availability solutions is the Oracle Application Server disaster recovery solution. the. (For complete disaster recovery and data protection, use the architecture shown in Figure 7-8.). Clients are connected to the logical standby database and can work with its data. Longer detection time usually leads to longer recovery time required to repair the appropriate transactions. 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 . At a high level, Oracle Application Server local high availability architectures include several active-active and active-passive architectures for the OracleAS middle-tier and the OracleAS Infrastructure. They will enhance your knowledge and help you to emerge as the best candidate. 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 allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. Table 7-3 Additional Capabilities of High Level Oracle High Availability Architectures, The foundation for all high availability architectures. 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. Fast-Start Fault Recovery bounds and optimizes instance and database recovery times to minutes. If the sub-clusters are of the different sizes, the functionality is same as earlier i.e. Footnote2Oracle ASM automatically rebalances stored data when disks are added or removed while the database remains online. Hence, to protect the integrity of the cluster and its data, the split-brain must be resolved. Configurations and data must be synchronized regularly between the two sites to maintain homogeneity. Figure 7-3 shows the Oracle Clusterware configuration after a cold cluster failover has occurred. 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. SELECT statements might be as straightforward as selecting a few . 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. With the Oracle Grid technologies, you can enable a high level of usage and low TCO without sacrificing business requirements. But 1 and 2 cannot talk to 3, and vice versa. To protect against site failures, the MAA recommends that Oracle RAC and Oracle Data Guard reside on separate systems (clusters) and data centers. 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. Oracle Data Guard is operating in a steady state, with the primary database transmitting redo data to the target standby database and the observer monitoring the state of the entire configuration.
Independence Heights Redevelopment Council,
Toombs Funeral Home Obituaries Muskegon,
Carnival Cruises Out Of Galveston,
Houses For Rent In West Columbia, Sc Under $700,
Is Hamilton Coming To Brisbane 2021,
Articles W
