Early Database Management Systems

Early Database Management Systems

The first commercial database management systems appeared in the late 1960's. These systems evolved from file systems, which offer some of item (3) above; file systems accumulate data over a long phase of time, and they allow the storage of huge amounts of data. However, file systems do not usually give assurance that data cannot be lost if it is not backed up, and they don't support well-organized access to data items whose location in a particular file is not known.

Further: file systems do not directly support item (2), a query language for the data in files. Their support for (1) - a diagram for the data - is limited to the formation of directory structures for files. Finally, file systems do not satisfy (4). When they allow simultaneous access to files by numerous users or processes, a file system usually will not avoid situations such as two users modifying the same file at about the same time, so the changes made by one user fail to emerge in the file.

The first important applications of DBMS's were ones where data was composed of many small items, and many queries or changes were made. Here are some of these applications.




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