Database development stage-file system Stage

The database history can be traced back to fifty years ago, when data management was very simple. Data is processed by a large number of classification, comparison, and table-drawn machines running millions of punched cards. The running results are printed on paper or made into new punched cards. Data management is to physically store and process all these punched cards. However, Remington Rand Inc .) A computer called Univac I introduced a tape drive that can input hundreds of records in one second, leading to a revolution in data management. In 1956, IBM produced the first disk drive, the Model 305 RAMAC. This drive has 50 disks, each of which is 2 feet in diameter and can store 5 MB of data. The biggest advantage of using a disk is that you can access data randomly, while punched cards and tapes can only access data sequentially.

1951: The Univac system uses tape and punched cards for data storage.

The database system emerged in 1960s. At that time, computers were widely used in data management and put forward higher and higher requirements for data sharing. Traditional file systems cannot meet people's needs. A Database Management System (DBMS) capable of unified management and data sharing came into being. The data model is the core and basis of the database system, and various DBMS software is based on a certain data model. Therefore, traditional database systems are usually divided into three types based on the characteristics of the data model: mesh database, hierarchical database, and relational database.

From the middle of the 1950s s to the middle of the 1960s S, the emergence of large-capacity computer storage devices (such as hard disks) has promoted the development of software technology, the emergence of the operating system marks a new stage of data management. In the file system stage, data is stored in external storage in a file unit and managed by the operating system in a unified manner. The operating system provides a user-friendly interface for users to use files. The logical structure of a file is decoupled from the physical structure, and the program and data are separated, so that the data and the program have a certain degree of independence. User programs and data can be separately stored in external memory, and each application can share a group of data, achieving data sharing in file units.

However, because the data organization is still program-oriented, a large amount of data redundancy exists. In addition, the logical structure of data cannot be easily modified and expanded. Every small change in the logical structure of data will affect the application. Because files are independent from each other, they cannot reflect the connections between things in the real world, and the operating system is not responsible for maintaining the contact information between files. If there is a relationship between files, it can only be processed by applications.