Let's talk about the process of Oracle query

Oracle query process

In the Oracle database, each user process is supported by an independent Oracle service process. These service processes are created and maintained by Oracle server processes. In such an architecture, the Oracle server process acts as a hypervisor responsible for maintaining, monitoring, and providing all processes connected to the database.

In order to obtain better system performance, Oracle allows multiple clients to establish connections with the same server process. However, in the case of multiple client connections, the Oracle server process must be able to identify each client's request to avoid confusion and ensure that each request is responded to correctly.

Types of Oracle processes

In Oracle, there are a total of 6 different types of processes.

1. Oracle server process

The Oracle server process is also called the Oracle daemon process. It is one of the most important processes in the Oracle database. The Oracle server process is the main process used to manage the entire database instance. It is responsible for processing requests passed by the user process and returning the query results to the user process.

2. Oracle background process

Oracle background process is an auxiliary process of the Oracle server process. They are responsible for performing some specific background tasks. Among them, the most important background processes are DBWn, LGWR and CKPT processes, which are respectively responsible for buffer management, log file refresh, and database backup and recovery operations.

3. User process

The user process refers to the client program that establishes a connection with the Oracle database server. When a user process sends query requests to the Oracle server, the Oracle server process will forward these requests to related background processes and other user processes to respond to the requests.

4. Database link process

The database link process refers to the process of transferring data between multiple different Oracle instances. These processes are automatically started when an Oracle client program wants to access a database that is distributed among multiple instances.

5. Monitoring process

The monitoring process is a process used to monitor, manage and release system resources. They can automatically monitor the system's disk space, CPU load, memory usage and other indicators, and can perform some related operations to avoid system resource bottlenecks.

6. External processes

External processes refer to those processes that have nothing to do with the Oracle database. They can be started from the operating system level and establish communication connections with the Oracle database to achieve specific tasks.

How to query the Oracle process

Querying the Oracle process can usually be done using Oracle's own diagnostic tool - Enterprise Manager Database Control. After entering Enterprise Manager, users can view all processes in the database instance through the following steps:

1. Open the "Database" tab and select the corresponding database instance;
2. Click "Performance" tab, and then click the "Top Activity" subtab;
3. In the "Top Activity" page, users can see a list of all currently running processes, as well as their detailed status information.

In addition to Enterprise Manager, you can also use the following methods to query the Oracle process:

1. Using SQL statements

By executing With the following SQL statement, users can view all running Oracle processes:

SELECT spid,username,program,osuser,status,sid,serial#,sql_id,sql_child_number FROM v$session;

2. Use operating system tools

Use the process management tools that come with the operating system, such as the ps tool on Unix and Linux platforms or the task manager on Windows platforms. Users can view the current process List of running processes. In these tools, you can locate the Oracle process by looking for processes containing the keyword oracle.

Summary

The operation of Oracle database depends on the coordination and cooperation of various processes. The Oracle daemon is the main process for maintaining the entire database instance, and with the assistance of other background processes, it can handle a large number of concurrent requests. By understanding the types and characteristics of these processes, users can better understand the internal operating mechanism of the Oracle database and improve their ability to manage its performance and stability.

The above is the detailed content of Let's talk about the process of Oracle query. For more information, please follow other related articles on the PHP Chinese website!