what is oraclerac

oracle rac refers to Oracle Real-time Application Cluster, which is a cluster database with a shared cache architecture. It overcomes the limitations of the traditional shared nothing method and shared disk method, and provides a user-friendly solution for all business applications. A highly scalable and available database solution.

The operating environment of this tutorial: Windows 7 system, Oracle 11g version, Dell G3 computer.

What is Oracle RAC

Oracle RAC (real application clusters, "real-time application clusters") is a cluster database with a shared cache architecture , which overcomes the limitations of traditional shared-nothing and shared-disk approaches, providing a highly scalable and available database solution for all your business applications. Oracle RAC is a key component of Oracle Private Cloud architecture.

Oracle RAC can eliminate the single point of failure problem of the database server, thereby providing customers with excellent database availability. In a clustered server environment, the database itself is shared across the server pool, which means that if any server in the pool fails, the database will continue to run on the healthy server. Oracle RAC not only allows customers to continue handling database workloads in the event of a server failure, but it also helps reduce downtime costs by reducing planned offline maintenance of the database.

Oracle RAC supports transparent deployment of Oracle databases on clustered server pools. This allows customers to easily redeploy Oracle Database on a single server to a cluster of database servers, taking advantage of the consolidated memory capacity and processing power provided by clustered database servers.

Oracle RAC provides all the necessary software components to allow you to easily deploy Oracle Database on a server pool and take full advantage of the performance, scalability and availability provided by the cluster. Oracle RAC leverages Oracle Grid Infrastructure as the foundation for the Oracle RAC database system. Oracle Grid Infrastructure includes Oracle Clusterware and Oracle Automatic Storage Management (ASM) to efficiently share server and storage resources in a highly available and scalable database cloud environment.

Advantages:

Oracle RAC mainly supports Oracle9i, 10g, 11g, and 12C versions, and can support 24 x 7 effective database application systems. Build a high-availability database system on low-cost servers 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) When the system planning and design is poor, the performance may not even be as good as a single node;

(3) It may increase the software cost (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.

What problem does rac solve

1. High availability: automatic switching, load balancing

2. High performance: multiple instances, more connections, concurrent execution

3. High expansion: expand nodes without downtime.

RAC architecture

##For RAC, there are at least two sets of physically different networks, private The network is specifically used for data exchange between instances. If all data is in a private network, it will affect the data and seriously affect the performance of RAC. Data is transferred between instances using a private network and a network provided by external services that are physically separated. Therefore, RAC has at least two sets of networks. One is for data transfer between instances, and the other is a public network that provides services to the outside world. External services provide IP links to the database from the public network.

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