Concurrent Use

A database system allows several users to access the database concurrently. Answering different questions from different users with the same (base) data is a central aspect of an information system.
Such concurrent use of data increases the economy of a system. Data capturing and data storage is not redundant, the system can be operated from a central control and the data can be updated more efficiently. Additionally, better use of the most often very expensive (geo) data can be made.

When using data concurrently the problem of how the system should behave if changes are made simultanteously (e.g. two different users with different applications change the same data simultaneously) needs to be solved. Additionally, there is a serious security risk, for example, in the realms of data protection.
In technical jargon changes to a database are called transactions. This term is explained later in this lesson.