Oracle has several instances

Oracle can have one instance or multiple instances, depending on application requirements and configuration. Single instance is suitable for small applications or environments with a small number of concurrent requests, while multi-instance is suitable for large applications or needs to handle a large number of concurrent requests. environment of. Oracle database under multi-instance configuration can achieve high availability and fault tolerance through cluster technology.

#The operating environment of this article: Windows 10 system, Oracle version 19c, DELL G3 computer.

Oracle is a powerful and widely used relational database management system (RDBMS). In Oracle, an instance represents a running database. Below I will answer questions about Oracle instances in detail.

Oracle database instance is a running environment composed of multiple background processes and memory structures. It is responsible for managing and controlling database access and operations. An Oracle database can run multiple instances at the same time. Each instance runs independently and has its own memory structure and background process.

The number of instances depends on the configuration and requirements of the Oracle database. Generally speaking, an Oracle database can have one or more instances, depending on the following factors:

Single instance database: An Oracle database only runs one instance. This configuration is suitable for small applications or environments that only need to handle a small number of concurrent requests.

Multi-instance database: An Oracle database can run multiple instances. Multi-instance configurations are suitable for large applications or environments that need to handle a large number of concurrent requests. Each instance can run independently and provide services for different applications, thereby improving the performance and scalability of the database.

In a multi-instance configuration, each instance has its own SGA (System Global Area) and PGA (Program Global Area). SGA is the shared memory area of ​​the instance, used to store database buffers, redo log buffers, shared pools, etc. PGA is a private memory area for each user process and is used to store data and variables for user processes and server processes.

Oracle database under multi-instance configuration can achieve high availability and fault tolerance through cluster technology. By using clustering software (such as Oracle Real Application Clusters, or RAC for short), multiple instances can run on different physical servers to achieve load balancing and failover.

To summarize, Oracle database can have one or more instances, depending on application requirements and configuration. Single instance is suitable for small applications or environments with a small number of concurrent requests, while multi-instance is suitable for large applications or environments that need to handle a large number of concurrent requests. Oracle database under multi-instance configuration can achieve high availability and fault tolerance through cluster technology.

The above is the detailed content of Oracle has several instances. For more information, please follow other related articles on the PHP Chinese website!