what is oracle rac

RAC is the abbreviation of real application clusters, translated as "real-time application cluster". It is a new technology used in the new version of Oracle database. It is a type of high availability and is also the reason why Oracle database supports grid computing environment. Core Technology.

RAC is the abbreviation of real application clusters, translated as "real-time application cluster". It is a new technology used in the new version of Oracle database and is highly available. One is also the core technology of Oracle database to support grid computing environment.

Advantages

Oracle RAC mainly supports Oracle9i, 10g, 11g, and 12C versions, and can support 24 x 7 effective database application systems on low-cost servers. Build a high-availability database system on top of it and deploy applications freely without modifying the code.

In the Oracle RAC environment, Oracle integration provides cluster software and storage management software, reducing application costs for users. When the application scale needs to be expanded, users can expand the system as needed to ensure system performance.

(1) Multi-node load balancing;

(2) Provide high availability: fault tolerance and seamless switching functions to minimize the impact of hardware and software errors;

(3) Improve transaction response time through parallel execution technology--usually used for data analysis systems;

(4) Increase the number of transactions and connections per second through horizontal expansion--usually for Online transaction system;

(5) Save hardware costs, you can use multiple cheap PC servers to replace expensive minicomputers or mainframes, while saving corresponding maintenance costs;

(6) Expandable It has good performance and can easily add and delete nodes and expand hardware resources.

Disadvantages

(1) Compared with a single machine, the management is more complex and the requirements are higher;

(2)The performance when the system planning and design is poor Not even as good as a single node;

(3) may increase software costs (if you use a high-configuration PC server, Oracle generally charges based on the number of CPUs).

Before Oracle9i, the name of RAC was OPS (Oracle parallel Server). A big difference between RAC and OPS is that RAC uses Cache Fusion (cache merging) technology. In OPS, data requests between nodes require the data to be written to disk before the requesting node can read the data. When using Cache fusion, the data buffers of each RAC node transmit data blocks through the high-speed, low-latency internal network.

Component

In an application environment, all servers use and manage the same database. The purpose is to disperse the workload of each server. The hardware is at least More than two servers are required, and a shared storage device is also required. At the same time, two types of software are required, one is cluster software, and the other is the RAC component in the Oracle database. At the same time, the OS on all servers should be of the same type of OS. According to the load balancing configuration policy, when a client sends a request to the listener of a certain service, the server will send the request to the listener according to our load balancing policy. The local RAC component processing may also be sent to the RAC component processing of another server. After processing the request, RAC will access our shared storage device through the cluster software.

Looking at the logical structure, each node participating in the cluster has an independent instance (database instance), and these instances access the same database. Nodes communicate with each other through the communication layer of the cluster software. At the same time, in order to reduce IO consumption, a global cache service exists, so each database instance retains the same database cache.

【Related learning recommendations: oracle database learning tutorial】

The above is the detailed content of what is oracle rac. For more information, please follow other related articles on the PHP Chinese website!