Introduction to Oracle Process Structure

Oracle process structure is a strange concept for many new users who have just been familiar with Oracle databases. The following describes the knowledge of Oracle process structure for your reference.

A process is a mechanism in the operating system that can perform a series of operation steps. In some operating systems, the term JOB or TASK is used. A process usually has its own dedicated storage zone. The architecture design of the ORACLE process maximizes performance.

There are two types of ORACLE instances: single-process instances and multi-process instances.

A single process (ORACLE) is a database system that executes all ORACLE code. Because the ORACLE part and the customer application cannot be executed by processes separately, the ORACLE code and the user's database application are executed by a single process.

Only one user can access an ORACLE instance in a single process environment. For example, running ORACLE on a MS-DOS.

Multi-process ORACLE instances, also known as multi-user ORACLE, use multiple processes to execute different parts of ORACLE. Each connected user has a process.

In a multi-process system, processes are divided into two types: User processes and ORACLE processes. When a user runs an application, such as a PRO * C program or an ORACLE tool such as SQL * PLUS), a user process is created for the application that the user runs. There are two types of ORACLE processes: Server Processes and background processes. Server processes are used to process requests from user processes connected to the instance. When the application runs on the same machine instead of the network, the user process and the corresponding server process are generally combined into a single process to reduce system overhead. However, when the application and ORACLE run on different machines, the user process communicates with ORACLE through a separate server process. It can perform the following tasks:

Analyze and execute the SQL statements issued by the application.

When the necessary data block is read from the disk data file) to the shared database buffer of the SGA ).

Return the result to the application for processing.

To ensure better performance and better coordination among multiple users, the system uses some additional processes in a multi-process system, which are called background processes. In many operating systems, background processes are automatically created when the instance is started. An ORACLE instance can have many background processes, but they do not exist all the time.

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