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This article mainly explains "what is the structure of Oracle". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn what the Oracle structure is like.

I. Overview of database architecture

Oracle Server consists of two entities: an instance (instance) and a database (database).

1. Instance: an instance is a set of processes and memory structures initialized when the database is started

2. Database: database refers to some physical files in which users store data

The two entities are independent, but connected. During the database creation process, the instance is created before the database is created. In a typical single-instance environment, the relationship between instance and database is one-to-one, one instance is connected to a database, and the relationship between instance and database can also be many-to-one, that is, multiple instances on different computers open a common database on a shared disk system. This many-to-one relationship, known as practical Application Cluster (Real Application Clusters,RAC) RAC, greatly improves database performance, fault tolerance, and scalability (which may consume more storage space) and is an essential part of the oracle grid concept.

Second, the interactive process

1. Interaction between user and user process

User processes can be general client software, such as Oracle's sqlplus,sql developer, or some drivers, etc., all belong to user processes.

2. Interaction between user process and server process

The server process is sometimes called the foreground process, of course, compared to the background process (database writer, log writer, etc., which will be mentioned later), the main function of the server process is to process the request of the user process connected to the current instance, execute the sql sent by the client and return the execution result. In the proprietary server structure, the user process and the server process are one-to-one, that is, when the listener listens to a request from the client, it will assign a corresponding server process to it. Another structure is the shared server, which is not a user process corresponding to a server process, but will be coordinated by the scheduler. I will not repeat the shared server connection in this article.

3. The server process interacts with the instance process

4. Interaction between instance and database process

At this point, I believe you have a deeper understanding of "what the structure of Oracle is". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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