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The description of how the database is physically stored is called "internal schema". The internal mode gives the physical storage structure and physical access methods of the database, such as the file structure, index, cluster and hash of the data storage, and the access path. The physical nature of the internal mode is mainly reflected in the operating system and file level.

Internal mode (Internal Schema), also known as physical mode (Physical Schema), gives the physical storage structure and physical access methods of database, such as file structure, index, cluster, hash and other access modes and access paths of data storage. The physics of internal mode is mainly reflected in the operating system and file level.

The internal mode, also known as the storage mode, corresponds to the physical level, which is the internal representation or bottom description of all the data in the database, and the logical description of the lowest level of the database. It describes the storage mode and physical structure of the data on the storage medium, and corresponds to the database actually stored on the external storage medium.

The internal schema describes and defines all internal record types, the organization of indexes and files, and the details of data control by the internal schema description language, which is the storage view of the database.

The internal schema is the description and expression of the specific implementation of the database on the physical memory. It defines the physical organization of data on the storage medium, record addressing technology, and defines the size of physical storage data blocks, overflow processing methods, and so on.

Corresponding to the conceptual schema, the internal schema is described by the data storage description language. The three-level schema structure of the database system distinguishes the global logical structure from the physical storage structure of the database, which brings convenience to the organization and use of the database. Different users can have their own data views. The data views of all users are organized together to get the global data view.

Use the storage description language to define and describe the global data view data, and store the data on the physical medium.

There are two images in between:

One is the mapping between the external schema and the conceptual schema, which defines the corresponding relationship between them and ensures the logical independence of the data.

The other is the mapping between the conceptual schema and the internal schema, which defines the corresponding relationship between the logical structure of the data and the physical storage, which makes the global logical data independent of the physical storage and ensures the physical independence of the data.

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