Updating your database development
DBMSs are found at the heart of most database applications.DBMSs may be built around a custom multitasking kernel with built-in networking support, but modern DBMSs typically rely on a standard operating system to provide these functions.However, since their development cost can be spread over a large number of users, they are often the most cost-effective approach.On the other hand, a general-purpose DBMS may introduce unnecessary overhead.Application software can often access a database on behalf of end-users, without exposing the DBMS interface directly.Application programmers may use a wire protocol directly, or more likely through an application programming interface.
DBMS may become a complex software system and its development typically requires thousands of human years of development effort.
Databases are used to support internal operations of organizations and to underpin online interactions with customers and suppliers (see Enterprise software).
Databases are used to hold administrative information and more specialized data, such as engineering data or economic models.
Therefore, many systems use a special-purpose DBMS.
A common example is an email system that performs many of the functions of a general-purpose DBMS such as the insertion and deletion of messages composed of various items of data or associating messages with a particular email address; but these functions are limited to what is required to handle email and don't provide the user with all of the functionality that would be available using a general-purpose DBMS.
The relational model employs sets of ledger-style tables, each used for a different type of entity.