Physical models including conceptual model of how data stored in computer memory in the two specifications。 Analysts and the database design is as important to the physical database (physical mode) definition, it provides information on the distribution and management of data storage and access of the physical memory space of two full database technology specifications。

Database development and database technology database is among the three models pided into basis。 Database development projects may have a role  to  only deal with these three views of a related work。 For example, a beginner may be designed for one or more procedures external model, and an experienced developer will design the physical model or conceptual model。 Database design issues at different levels are quite different。

4three-tier structure of the database positioning system

Obviously, all the good things in the database are, and the "three"!

When designing a database, you have to choose where to store data。 This option in the physical database design stage。 Database is pided into inpidual databases, the  Working  Group database,  departmental databases,  corporate databases  and   the

Internet database。 Inpiduals often by the end-user database design and development of their own, just by database experts to give training and advice to help, it only contains inpidual end-users interested in the data。 Sometimes, personal database from the database or enterprise Working Group extracted from the database, such circumstances database prepared by some experts from the regular routine to create local database。 Sector Working Group database and the database is often the end-user, business experts and the central database system experts development。 The collaborative work of these officers is necessary because in the design of the database to be shared by a large number of issues weigh: processing speed, ease of use, data definition differences and other similar problems。 Due to corporate databases and the Internet database broad impact, large-scale, it is normally concentrated in the database development team has received professional training to develop a database of experts。

1。Customers layer

A desktop or notebook also known as that layer, which specialized management user interface and system localization data in this layer can be implemented on  the Web scripting tasks。

2。Server / Web server

HTTP protocol handling, scripting tasks, the implementation of computing and provide data access, the layer known as processing services layer。

3。Enterprise Server (Minicomputer or mainframe) layer

The implementation of complex computing and inter-organizational management from multiple data sources of data integration, also known as data services layer。

In an organization, hierarchical database and information system architecture for distributed computing and the client / server architecture of the concept of correlation。 Client / server architecture based on a LAN environment, including servers (referred to as database server or database engine) database software implementation from the client workstation database orders, each customer applications focus on their user interface functions。 In fact, the whole concept of the database (as well as the application of these databases to handle routine) as a distributed database or the separate but related physical database distribution in the local PC workstation, server intermediate (working group or sector) and one center server (departments or enterprises )。 Simply said that the use of client / server architecture for:

●it can handle multiple processors on the same application at the same time, improve application response time and data processing speed。

●It can use each computer platform of the best data processing (such as PC Minicom Advanced user interface with the mainframe and computing speed)。