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. For storage migration, you are required to use both storage arrays by Oracle ASM temporarily. 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. Oracle Data Guard transmits redo data from the primary database to the secondary site to keep the databases synchronized. 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. Oracle Enterprise Manager support for patch application simplifies software maintenance. The problem which could arise out of this situation is that the sane . All single-instance high availability features, such as the Flashback technologies and online reorganization, also apply to Oracle RAC. Figure 7-2 Oracle Database with Oracle Clusterware (Before Cold Cluster Failover). Following the execution of a SELECT statement, a tabular result is held in a result table (called a result set). 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. This chapter describes the various high availability architectures in an Oracle environment and helps you to choose the correct architecture for your organization. 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. It requires only a standard TCP/IP-based network link between the two computers. Oracle Flashback Technology optimizes logical failure repair. It allows you to select the table columns depending on a set of criteria. host01 is evicted although it has a lower node number. You should adopt the MAA best practices to achieve the optimal recovery time and configuration. 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)). Uses a private network and voting disk-based communication to detect and resolve split-brainFoot2 scenarios. A highly available and resilient application requires that every component of the application must tolerate failures and changes. At the logical standby database, the redo data is transformed into SQL statements, which are applied to the logical standby database. If your business does not require the scalability and additional high availability benefits provided by Oracle RAC, but you still need all the benefits of Oracle Data Guard and cold cluster failover, then Oracle Database with Oracle Clusterware and Oracle Data Guard is a good compromise architecture. Oracle Flashback Technology optimizes logical failure repair. 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. Simulate loss of connectivity between two nodes. 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. 3. For high availability, Oracle recommends that you have a minimum of three voting disks. 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/. 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. Additional protection from data center failure with special considerations that are documented in Section 7.1.4.1, Highest level of availability for server or computer room failure. If all the sub-clusters are of the same size, the functionality has been modified as: If the sub-clusters have equal node weights, the sub-cluster with the lowest numbered node in it survives so that, in a 2-node cluster, the node with the lowest node number will survive. Consider using Oracle Database with Oracle GoldenGate if one or more of the following conditions are true: Updates are required on both sites or databases, and the changes must be propagated bidirectionally. Another possible configuration might be a testing hub consisting of snapshot standby databases. 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. 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. Footnote8With automatic block repair, this should be the most common block corruption repair. Oracle RAC allows multiple computers to run Oracle RDBMS software simultaneously while accessing a single database, thus providing clustering. For more information, see Oracle Data Guard Concepts and Administration or the Oracle Streams Replication Administrator's Guide. This configuration consists of a central resource supporting 10 applications and databases in the grid, rather than managing 10 separate system or storage units in a nongrid infrastructure. Why is it like that? Section 7.1.8 describes how you can achieve the highest level of availability with Oracle RAC and Oracle Data Guard. For example, Table 7-1 provides some insight into the probability of different outages during unplanned and planned activities. Fine control of information and data sharing are required. Oracle Application Server provides redundancy by offering support for multiple instances supporting the same workload. Applications can easily mask failures to the end user. Table 7-2 High Availability Architecture Recommendations. Limited support for mixed platforms. The Oracle Data Guard broker communicates with the production database, the physical standby database, and the logical standby database. In this article I will explore this new feature for one of the possible factors contributing to the node weight, i.e. The combination of Oracle RAC and Oracle Data Guard provide the most comprehensive architecture for reducing downtime for scheduled outages and preventing, detecting, and recovering from unscheduled outages. Figure 7-8 shows an Oracle Clusterware and Oracle Data Guard architecture that consists of a primary and a secondary site. These devices convert ESCON or Fibre Channel to the appropriate IP, ATM, or SONET networks. Support for bidirectional replication and updating anything and anywhere. These figures show how you can use the Oracle Clusterware framework to make both Oracle Database and your custom applications highly available. Fast-Start Fault Recovery bounds and optimizes instance and database recovery times to minutes. Building on top of the local high availability solutions is the Oracle Application Server disaster recovery solution. 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. This book focuses primarily on the database high availability solutions. You can define multiple application VIPs, with generally one application VIP defined for each application running. Clusterware will evaluate cluster resources on implied workload 3. . 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. 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". 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. 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. For example, you can put the files on different disks, volumes, file systems, and so on. 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 operate independently of each other. However, starting from Oracle Database 12.1.0.2c, the node with higher weight will survive during split brain resolution. (adsbygoogle=window.adsbygoogle||[]).push({}); The biggest risk following a Split-Brain event is the potential for corrupting system state. 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. If the sub-clusters are of the different sizes, the clusterware identifies the largest sub-cluster, and aborts all the nodes which do. Now talking about split-brain concept with respect to oracle . 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. Chapter 2 describes how the high availability requirements for the business plus its allotted budget determine the appropriate architecture. 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. Oracle Database with Oracle RAC architecture provides the following benefits over a traditional monolithic database server and the cold cluster failover model: Flexibility to increase processing capacity using commodity hardware without downtime or changes to the application, Ability to tolerate and quickly recover from computer and instance failures (measured in seconds), Optimized communication in the cluster over redundant network interfaces, without using bonding or other technologies. pagespeed.lazyLoadImages.overrideAttributeFunctions(); Figure 7-6 shows the relationships between the primary database, target standby database, and the observer before, during, and after a fast-start failover. Maximum RTO for instance or node failure is in seconds to minutes. You should determine if both sites are likely to be affected by the same disaster. 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. Figure 7-7 shows the production database at the primary site and multiple standby databases at secondary sites.