Oracle RAC & Overview of Oracle RAC

 

Oracle RAC (Real Application Cluster) : 

 

RAC stands for Real Application Clusters. It’s a high availability solution for Oracle DB. Here two or more nodes (instances) are clustered as a single DB by using shared disks. So, there’s no single point of failure from the DB side. A cluster comprises different interconnected computers or servers that show up as in case they are one server to conclusion clients and applications. Oracle RAC empowers you to cluster Oracle databases. 

Oracle RAC employments Oracle Cluster ware for the foundation to tie numerous servers so they work as a single system. Oracle Cluster ware may be a convenient cluster administration arrangement that coordinates with Oracle Database. Oracle Cluster ware is additionally a required component for utilizing Oracle RAC. In expansion, Oracle Cluster ware empowers both single-instance Oracle databases and Oracle RAC databases to utilize the Oracle high-availability foundation. Oracle Cluster ware empowers you to make a clustered pool of capacity to be utilized by any combination of single-instance and Oracle RAC databases. 

RAC architecture

Applications of RAC 

• Autonomous Health Framework 

• Oracle Application Continuity 

• Oracle Database Quality of Service Management 

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Features of RAC 

• High Availability 
  Real Application Clusters gives clients the most noteworthy database accessibility by expelling person database servers as a single point of failure. In a clustered server environment, the database itself is shared over a pool of servers, which suggests that on the off chance that any server within the server pool falls flat, the database proceeds to run on surviving servers. Oracle RAC not only empowers clients to proceed to prepare database workloads within the occasion of a server disappointment, it too makes a difference to assist decrease costs of downtime by lessening the sum of time databases are taken offline for arranged upkeep operations.

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• Database as a Service 
  Real Application Clusters gives all the computer program components required to effectively send Oracle Databases on a pool of servers and take full advantage of the execution, versatility, and accessibility that clustering gives. Oracle RAC utilizes Oracle Grid Framework as the establishment for Prophet RAC database frameworks. Oracle Network Foundation incorporates Oracle Cluster ware and Oracle Programmed Capacity Administration (ASM) that empowers the effective sharing of server and capacity assets in a profoundly accessible and adaptable database cloud environment. 

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Advantages OF RAC 

• Certain patches can be applied in its rolling mode. 
  In rolling fixing, each hub is closed down in Oracle RAC, at that point the fix is connected. Once that happens, the hub is brought back up once more. By going independently to each hub, a total shutdown is maintained a strategic distance from, which is why the uptime for this alternative is reliably at or close 100%. In spite of the fact that a few patches cannot be connected in this mode, you still have the least downtime fixing highlights that will still assist you to stay beneficial. 

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• It is load balanced for a better performance. 
  With Oracle RAC, the administrations facilitate their sessions by enrolling in their workload. They can too enlist the sum of work being taken care of. With this data, clients can be diverted to the least-loaded hub that’s running an occasion for their particular administrations. Two sorts of stack adjusting are included: client-side and server-side. This makes it conceivable to keep working at the speeds you require without the same dangers of data misfortune. 

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• Unless the connections are not RAC aware, there is no need for a reconnection. 
  Since Oracle RAC could be a node-based framework, impromptu disappointments make a negligible effect on the user when compared to comparable administrations. To preserve accessibility, clients who are associated with a fizzled occasion are promptly built up to a new connection with the surviving occasions inside the database. A reconnection isn’t vital beneath most circumstances since you’re basically moving your hub nearness. As long as the essential location remains intaglio, this advantage regularly remains. 

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• DML processes are able to roll back. 
  There are times when you’re working within the SQL Also environment when your information control dialect articulations don’t go as arranged. Rather than having your articulation gotten to be quickly changeless, this framework permits you to see the impact of a DML explanation in Engineer. It does not end up lasting until you total an exchange that incorporates it. 

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Disadvantage of RAC 

• It requires a specific network configuration to work properly 
  With Oracle RAC, you must have your Check IPs, your VIPs, and your open IP addresses all on the same open arrange for the database to function appropriately. The private IPs must be on a diverse arrange than the open organize. You must have your private and open IPs be pingable sometime recently the establishment starts. In case one link in this chain isn’t input, at that point, you may create an erroneous organize arrangement mistake. 

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• You must have Oracle RAC on shared storage 
  With Oracle RAC, you must have your database records, your OCR area, and your voting disk all on shared capacity. In the event that you are doing not, at that point it’ll not work appropriately. Any issue that you simply have with the shared disk arrangement will inevitably cause the framework to fall flat, which creates an erroneous shared disk setup blunder report. 

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• lot of prerequisites that must be completed. 
  After you design the organize for Oracle RAC and Cluster ware, you’ll find that each hub within the cluster has particular prerequisites that must be met. You must have at slightest 2 arrange interface cards, open interface names for each hub, and the same private interface names for all hubs as well. You arrange connector must back TCP/IP and the private interface must bolster UDP for high-speed organize connectors with a switch that underpins gigabit ethernet at least. 

 

Overview of Oracle RAC : 

 

Noncluster Oracle databases have a one-to-one relationship between the Oracle database and the instance. Oracle RAC environments, however, have a one-to-many relationship between the database and instances. An Oracle RAC database can have up to 100 instances, all of which access one database. All database instances must use the same interconnect, which can also be used by Oracle Cluster ware. 

Oracle RAC databases differ architecturally from noncluster Oracle databases in that each Oracle RAC database instance also has: 

• At least one additional thread of redo for each instance 

• An instance-specific undo tablespace 

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The combined processing power of the multiple servers can provide greater throughput and Oracle RAC scalability than is available from a single server. 

A cluster comprises multiple interconnected computers or servers that appear as if they are one server to end users and applications. The Oracle RAC option with Oracle Database enables you to cluster Oracle databases. Oracle RAC uses Oracle Cluster ware for the infrastructure to bind multiple servers so they operate as a single system. 

Oracle Cluster ware is a portable cluster management solution that is integrated with Oracle Database. Oracle Cluster ware is a required component for using Oracle RAC that provides the infrastructure necessary to run Oracle RAC. Oracle Cluster ware also manages resources, such as Virtual Internet Protocol (VIP) addresses, databases, listeners, services, and so on. In addition, Oracle Cluster ware enables both noncluster Oracle databases and Oracle RAC databases to use the Oracle high-availability infrastructure. Oracle Cluster ware along with Oracle Automatic Storage Management (Oracle ASM) (the two together comprise the Oracle Grid Infrastructure) enables you to create a clustered pool of storage to be used by any combination of noncluster and Oracle RAC databases. 

Oracle Cluster ware is the only cluster ware that you need for most platforms on which Oracle RAC operates. If your database applications require vendor cluster ware, then you can use such cluster ware in conjunction with Oracle Cluster ware if that vendor cluster ware is certified for Oracle RAC. 

Oracle Database with Oracle RAC Architecture

An Oracle RAC environment is located in one data center. However, you can configure Oracle RAC on an extended distance cluster, which 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 a single database cluster. In an extended cluster, the nodes in the cluster are typically dispersed, geographically, such as between two fire cells, between two rooms or buildings, or between two different data centers or cities. For availability reasons, the data must be located at both sites, thus requiring the implementation of disk mirroring technology for storage. 

If you choose to implement this architecture, you must assess whether this architecture is a good solution for your business, especially considering distance, latency, and the degree of protection it provides. Oracle RAC on extended clusters provides higher availability than is possible with local Oracle RAC configurations, but an extended cluster may not fulfill all of the disaster-recovery requirements of your organization. A feasible separation provides great protection for some disasters (for example, local power outage or server room flooding) but it cannot provide protection against all types of outages. For comprehensive protection against disasters—including protection against corruptions and regional disasters—Oracle recommends the use of Oracle Data Guard with Oracle RAC, as described in the Oracle Database High Availability Overview and on the Maximum Availability Architecture (MAA). 

Oracle RAC is a unique technology that provides high availability and scalability for all application types. The Oracle RAC infrastructure is also a key component for implementing the Oracle enterprise grid computing architecture. Having multiple instances access a single database prevents the server from being a single point of failure. Oracle RAC enables you to combine smaller commodity servers into a cluster to create scalable environments that support mission critical business applications. Applications that you deploy on Oracle RAC databases can operate without code changes.