All Oracle RAC nodes can be active by implementing multiple Oracle RAC One Node configurations for different databases. Footnote2Oracle ASM automatically rebalances stored data when disks are added or removed while the database remains online. Configuring symmetric sites is recommended to ensure that each site can accommodate the performance and scalability requirements of the application after any role transition. Configurations and data must be synchronized regularly between the two sites to maintain homogeneity. Oracle Data Guard is designed to allow businesses get something useful out of their expensive investment in a disaster-recovery site. This has the potential for data corruption. As the result, 1 or more instance(s) will be evicted. The group(cohort) with lower node member survive, in case of same number of node(s) available in each group. Table 7-3 Additional Capabilities of High Level Oracle High Availability Architectures, The foundation for all high availability architectures. At the time of role transition, more storage and system resources can be allocated toward that application. Clients on the network experience a period of lockout while the failover occurs and are then served by the other database instance after the instance has started. Support for heterogeneous platforms, versions, and character sets. The common voting result will be: a. Oracle Data Guard transmits redo data from the primary database to the secondary site to keep the databases synchronized. 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. Maximum RTO for instance or node failure is zero for the databaseFootref1. The production database transmits redo data (either synchronously or asynchronously) to redo log files at the physical standby database. Customer can designate which server(s) and resource(s) are critical 2. Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. The following sections provide an overview of Oracle Database high availability architectures and implement the MAA best practices: Oracle Database with Oracle Clusterware (Cold Cluster Failover), Oracle Database with Oracle Real Application Clusters (Oracle RAC), Oracle Database with Oracle Clusterware and Oracle Data Guard, Oracle Database with Oracle RAC One Node and Oracle Data Guard, Oracle Database with Oracle RAC and Oracle Data Guard. The processes that were once co-operating prior to the Split-Brain event occurring, independently modify the same logically shared state, thus leading to conflicting views of system state. Fine control of information and data sharing are required. In a "split brain" situation, voting disk is used to determine which node (s) will survive and which node (s) will be evicted. Split brain scenario - RAC and PXC. Split brain syndrome occurs when the instances in a RAC fails to connect or ping to each other via the private interconnect. Network addresses are failed over to the backup node. In Oracle RAC, all the instances/servers communicate with each other using a private network. 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. 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. Starting from 12.1.0.2, during split brain resolution, the new algorithm followed to decide the nodes to be evicted/retained is as follows: Fortnightly newsletters help sharpen your skills and keep you ahead, with articles, ebooks and opinion to keep you informed. In an Oracle cluster prior to version 12.1.0.2c, when a split brain problem occurs, the node with lowest node number survives. Footnote2Rolling upgrades with Oracle Data Guard incur minimal downtime. Q39) Mention what is split brain syndrome in RAC? Oracle Flashback Technology optimizes logical failure repair. 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. c. Some improvement has been made to ensure node(s) with lower load survive in case the eviction is caused by high system load. 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". Node 1 is connected to Node 2 and to the Oracle database, but Node 1 is currently idle, in standby mode. 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. Where two or more instances . In such a scenario, integrity of the cluster and its data might be compromised due to uncoordinated writes to shared data by independently operating nodes. 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 . This architecture is referred to as an extended cluster. The solutions introduced in this book are described in detail in the Oracle Fusion Middleware High Availability Guide. Rolling upgrades for system and hardware changes, Rolling patch upgrades for some interim patches, security patches, CPUs, and cluster software, Fast, automatic, and intelligent connection and service relocation and failover, Comprehensive manageability integrating database and cluster features with Grid Plug and Play and policy-based cluster and capacity management, Load balancing advisory and run-time connection load balancing help redirect and balance work across the appropriate resources. Suppose there are 3 nodes in the following situation. Online Patching allows for dynamic database patches for diagnostic and interim patches. 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. Rolling upgrade for system, clusterware, operating system, CPUs, and some Oracle interim patches. Furthermore, operational practices across role transitions are simplified when the sites are symmetric. Footnote3Recovery time consists largely of the time it takes to restore the failed system. You should adopt the MAA best practices to achieve the optimal recovery time and configuration. At the logical standby database, the redo data is transformed into SQL statements, which are applied to the logical standby database. 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. Figure 7-1 Single-Node, Nonclustered Oracle Database with an Oracle ASM Instance. When the two data centers are located relatively close to each other, extended clusters can provide great protection for some disasters, but not all. 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. The problem which could arise out of this situation is that the sane . Fast-Start Fault Recovery bounds and optimizes instance and database recovery times to minutes. 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. which node first joined the cluster). Oblivious of the existence of other cluster fragments, each sub-cluster continues to operate independently of the others. Then there are two cohorts: {1, 2} and {3}. (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. It supports bidirectional replication, data transformations, subsetting, custom apply functions, and heterogeneous platforms. 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. 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 . There are numerous high availability features that you can use in the Oracle Database single-instance database architecture. If the fast recovery area is on the source volume that is remotely mirrored, then you must also remotely mirror the flashback logs. Rolling upgrade for system, clusterware, operating system, database, and application. Any database in a Data Guard configuration, whether a primary or standby database, can be an Oracle One Node database. Figure 7-7 shows the production database at the primary site and multiple standby databases at secondary sites. Split Brain: Whats new in Oracle Database 12.1.0.2c? Outages or data loss that could affect customer service and safety are avoided by using Oracle Data Guard synchronous transport and automatic failover (fast-start failover). 1. Nodes 1,2 can talk to each other. Table 7-5 Attainable Recovery Times for Planned Outages, System change - Dynamic Resource Provisioning. 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. These devices convert ESCON or Fibre Channel to the appropriate IP, ATM, or SONET networks. Any of these processes experience IPC Send time out will incur communication reconfiguration and instance eviction to avoid split brain. Fully supports Oracle Data Guard. An architecture that combines Oracle Database with Oracle RAC is inherently a highly available system. 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 Automatic Storage Management (Oracle ASM) and Oracle Automatic Storage Management Cluster File System (Oracle ACFS) tolerate storage failures and optimize storage performance and usage. 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. Oracle Database with Oracle GoldenGate provides granularity and control over what is replicated and how it is replicated. 1. 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. In the figure, the configuration is operating in normal mode in which Node 1 is the active instance connected to Oracle Database that is servicing applications and users. Figure 7-1 shows a basic, single-node Oracle Database that includes an Oracle ASM instance.Foot1 This architecture incorporates several high availability features, including Flashback Database, Online Redefinition, Recovery Manager, and Oracle Secure Backup. Rolling upgrade and patch capabilities for Oracle Clusterware with zero database downtime. Whatever the case, these Oracle RAC interview questions and answers are for you. 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. What is split brain in Oracle RAC? 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. The operation of an Oracle Clusterware cold cluster failover is depicted in Figure 7-2 and Figure 7-3. This chapter describes the various high availability architectures in an Oracle environment and helps you to choose the correct architecture for your organization. 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 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. 12) Mention what is split brain syndrome in RAC? However, when you use Oracle Clusterware, there is no need or advantage to using third-party clusterware. 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.
Northern Lakes League Records,
Articles W