The Oracle memory structure contains two memory zones

The Oracle memory structure contains two memory zones, which are also called shared global zones. During actual operations, these two memory zones are mainly used to store database information, the process is shared by N databases. The following is a detailed description of the process.

The Oracle memory structure contains the following two memory zones::

System global zone: SGA): This memory zone is allocated when the instance is started. The SGASystem Global Area of an Oracle instance is also called a shared Global Area. It is used to store database information and is shared by multiple database processes. When the database instance is started, the SGA memory is automatically allocated. SGA is the region with the largest server memory usage in the database and an important indicator that affects the database performance. Based on its function, SGA can be divided into a shared pool, data buffer zone, and log buffer zone.

Sharing pool

A shared pool is a memory region sharing pool that performs syntax analysis, compilation, and execution on SQL and PL/SQL programs. It consists of a database cache and a data dictionary cache. The size of the Shared Pool directly affects the database performance.

Data Buffer Zone

It is used to store the data read from the disk data file, which is shared by all users. The server process saves the read data in the data buffer. When subsequent requests need the data, they can be found in the memory and no longer need to read the data from the disk, improving the reading speed. The size of the data buffer has a direct impact on the reading speed of the database.

Log Buffer

Logs record all modification information of the database. The log information is first generated in the log buffer zone. When the number of log data in the log buffer reaches a certain level, the background process writes the log data to the log file. Relatively speaking, the log buffer has little impact on the database performance.

Program global zone: PGA): This memory zone is allocated when the server process starts. Program Global Area PGAProgram Global Area) contains the data and control information required by a single server process or a single background process. PGA is automatically allocated when a user process connects to the database and creates a session. This region retains the memory required by each user process connected to the Oracle database. The PGA is not a shared zone and can only be used by a single process. When a user session ends, the PGA is released.

The above content is an introduction to the Oracle memory structure. I hope you will get some benefits.