Oracle System Overview-memory structure

The memory structure is one of the most important components of the Oracle service system and a key element that determines the overall performance of the Oracle server. Size of SGA during Oracle server running

The memory structure is one of the most important components of the Oracle service system and a key element that determines the overall performance of the Oracle server. Size of SGA during Oracle server running

The memory structure is one of the most important components of the Oracle service system and a key element that determines the overall performance of the Oracle server. During the running process of the Oracle server, the SGA size directly affects the server's execution speed. Especially when the number of login users increases, the server must have enough memory to support it, otherwise, the query speed may be reduced and you may not be able to connect to the server.

Related reading:

Oracle System Overview-Data Dictionary

Oracle System Overview-instances

Oracle System Overview-memory structure

Overview of Oracle Server Architecture

Memory Structure composition

The Oracle memory structure is mainly divided into two parts:

(1) System Global Area (SGA ). SGA is a memory area allocated when an Oracle instance starts. The data and information it stores can be shared by the Oracle instance. Therefore, SGA becomes a shared memory area.

(2) Program Global Area (PGA ). PGA is a memory area allocated when an Oracle process starts. It stores private data and control information of background processes or server processes. Each process is associated with its own PGA, therefore, it is also called a non-shared memory zone.

The memory structure of the Oracle instance is 1-1.

-1

The Oracle memory structure stores the data and program code required by the Oracle instance during the working process, mainly divided into the following categories:

* The parsed SQL statement and PL/SQL code.

* All session information for connecting to the database.

* Cache data, including data produced by SQL statements and PL/SQL programs and redo log data.

* Information Required for Oracle operation, such as data dictionary information.

* Information Required for Oracle process sharing and communication, such as lock information.

System global zone:

System Gloabl Area (SGA. The SGA and Oracle processes form an Oracle instance. When Oracle is started, an SGA is automatically allocated. When the instance is closed, the operating system recycles this memory area. Each Oracle instance has its own region.