Oracle Real Application Clusters (RAC): Scalability & High Availability

Oracle RAC achieves high availability and scalability through multi-node shared database storage. Its working principle includes load balancing, failover and dynamic node expansion to ensure efficient operation of the system and data consistency.

introduction

In today's data-driven world, the scalability and high availability of databases are no longer optional, but a necessity for enterprise survival. Oracle Real Application Clusters (RAC) As a member of the Oracle database family, Oracle Real Application Clusters (RAC) is a tool to solve these needs. This article aims to explore the performance of Oracle RAC in terms of scalability and high availability, help you understand how it works, and demonstrate its advantages and challenges in practical applications through practical experience and code examples.

Review of basic knowledge

Oracle RAC is a cluster technology that allows multiple database servers to share the same database storage, thereby enabling load balancing and failover. It is based on Oracle's shared storage architecture, allowing multiple nodes to access database files at the same time, achieving efficient data processing.

The core of Oracle RAC is its cluster management and resource management functions, which can dynamically adjust the load and ensure high availability and scalability of the system.

Core concept or function analysis

The definition and function of Oracle RAC

Oracle RAC achieves database scalability and high availability by combining multiple server nodes into a cluster. Its main functions include:

• Load balancing : Improves the processing power of the system by distributing workloads across multiple nodes.
• Failover : When a node fails, Oracle RAC can automatically transfer the load to other available nodes to ensure that service is not interrupted.
• Scalability : As business grows, the processing power of the database can be improved by adding nodes.

A simple Oracle RAC configuration example:

 -- Suppose we have two nodes, node1 and node2
-- Configure Oracle RAC cluster CREATE CLUSTER my_cluster (
  node1 AS PRIMARY,
  node2 AS SECONDARY
);

-- Add node to cluster ALTER CLUSTER my_cluster ADD NODE node3;

This example shows how to create a simple Oracle RAC cluster and add new nodes.

How it works

The working principle of Oracle RAC mainly includes the following aspects:

• Cache Fusion : Through the global caching mechanism, ensures the synchronization and consistency of data between different nodes.
• Global Resource Directory (GRD) : manages and coordinates access to resources in the cluster to ensure efficient utilization of resources.
• Instance Recovery : When a node fails, Oracle RAC will automatically initiate instance recovery to ensure data consistency and service availability.

The implementation principle of Oracle RAC involves complex technical details, such as:

• Time Complexity : Oracle RAC significantly reduces response time through parallel processing and load balancing when handling high concurrent requests.
• Memory Management : Oracle RAC effectively manages memory resources through shared storage and global caching, reducing memory overhead.

Example of usage

Basic usage

In Oracle RAC, creating and managing clusters is the basic operation. A basic cluster creation and management example:

 --Create cluster CREATE CLUSTER my_cluster (
  node1 AS PRIMARY,
  node2 AS SECONDARY
);

-- Start the cluster STARTUP my_cluster;

-- Stop cluster SHUTDOWN my_cluster;

These commands show how to create, start, and stop an Oracle RAC cluster.

Advanced Usage

Advanced usage of Oracle RAC includes dynamic load balancing and failover policies. An example of advanced usage:

 -- Configure dynamic load balancing ALTER SYSTEM SET load_balancing = 'ON';

-- Configure the failover policy ALTER SYSTEM SET failover_mode = 'BASIC' SCOPE = SPFILE;

-- Restart the database to apply changes to SHUTDOWN IMMEDIATE;
STARTUP;

These commands show how to configure advanced features of Oracle RAC, such as dynamic load balancing and failover policies.

Common Errors and Debugging Tips

When using Oracle RAC, you may encounter some common problems, such as node communication failure, data inconsistency, etc. Here are some common errors and their debugging tips:

• Node communication failure : Check the network configuration to ensure that all nodes can communicate with each other. Use crsctl check cluster command to check the cluster status.
• Data inconsistency : Ensure that the database versions on all nodes are consistent, and use dbms_repair package to fix the data inconsistency problem.

Performance optimization and best practices

In practical applications, it is crucial to optimize the performance of Oracle RAC. Here are some performance optimizations and best practices:

• Performance comparison : Compare performance differences in different configurations, such as performance comparison between single node and multiple nodes. Use awr report to analyze performance bottlenecks.
• Optimization effect : By adjusting load balancing policies and failover policies, significantly improve system performance. For example, enabling dynamic load balancing can reduce response time.

In terms of programming habits and best practices, the following principles are recommended:

• Code readability : Use clear comments and naming conventions to ensure that the code is easy to understand and maintain.
• Maintenance : Regularly check and update Oracle RAC configurations to ensure high availability and scalability of the system.

Through the discussion and examples in this article, I hope you can better understand the advantages of Oracle RAC in scalability and high availability, and flexibly use these technologies in practical applications.

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