In general, all database applications include: - Application processing components. - Database software components (Database software componets) - The database itself. The models of database processing are different because of the cases where the above three types of components are located. This article introduces five architecture models based on the distributed configuration of data access of computer systems Client / Server. - Centralized database model. - Model database file (server - database model). - Database extract processing model. - Client / Server database model (Client / Server database model) - Distributed database model (Distributed database model) 1. Centralized database model (Centralized database model) In this model, the application processing components, the database software, and the database itself are on a processor. For example, personal computer users can run application programs that use Oracle database software to access the database located on the hard disk of the individual computer. Since the application components, the database software and the database itself reside on a single computer, the application is compatible with the centralized model. Most of the main information flow processing is done by many organizations that still fit the focus model. For example, a mainframe processor running IBM's IMS or DB2 database software could provide workstations in locations that disperse rapid access to the central database. However, in many such systems, all three components of the database application are implemented on the same mainframe machine, so the configuration is well suited to the centralized model. Database model - server (File server - database model) In a file-server model, the application components and database software on a computer system and physical files form the database on another computer system. Such a configuration is usually used in a local environment in which one or more computer systems play the role of a server, storing data files for other computer systems. In the file-server environment, the network software is enforced and the application software as well as the database software running on the end-user system considers the files or databases on the actual file server. as on their own computer. The file server model is very similar to the centralized model. Database files reside on machines other than application components and database software; However, application components and database software may have the same design to operate a centralized environment. The fact that network software has made application software and database software think they are accessing the database in a local environment. Such an environment may be more complex than the centralized model because the network software may have to perform a concurrent mechanism that allows multiple end users to access the same database. Database model processing (Database extract processing model) Another model in which a remote database can be accessed by the database software is called partial data processing. With this model, the user can be at a personal computer connected to the remote computer system where the desired data is. The user can then directly interact with the software running on the remote machine and create a request to retrieve data from that database. Users can also transfer data from a remote computer to their own computer and to the hard disk and can perform the copying using the database software on the individual machine. With this approach, the user must know for sure where the data is and how to access and retrieve data from a remote computer. Bundled application software is required on both computer systems to control data access and data transfer between the two systems. However, database software running on two machines does not need to know that remote database processing is taking place because the user interacts with them independently. Database model Client / Server (Client / Server database model) In the Client / Server database model, the database resides on a different machine than the machine that has the application processing component. But the database software is split between the client system running the application programs and the database server system. In this model, the application processing components on the client system make the request for the database software on the client, the software will connect to the database software running on the server. Server database software will access the database and return results to the client. At first glance, the Client / Server database model looks like the file - server model, but the Client / Server model has many advantages over the file - server model. With the file-server model, information associated with physical database access must be run across the network. A transaction that requires multiple data access can cause traffic congestion on the network. Assume an end user creates a query to retrieve total data, which requires retrieving data from 1000 records, with the file - content server approach of all 1000 records placed on the network, Because the database software running on the user's machine must access each record to satisfy the user's requirements. With the Client / Server database approach, only the initial startup query and the end result need to be posted on the network, the database software running on the database server will access the database. Record them, process them and call the necessary procedures to produce the final results. Front-end software In the Client / Server database model, we often refer to front-end software and back-end software. Front-end software runs on a single PC or workstation and meets individual requirements, which play the role of Client in the Client / Server database application and perform functions. Toward end-user needs, front-end software is often divided into the following categories: End user database software: This database software can be made by end users on their own systems to access small local databases as well as connect to databases. Larger than on Server database. - Simple query and reporting software: This software is designed to provide easy-to-use tools for retrieving data from the database and generating simple reports from existing data. - Data analysis software: This software provides search and retrieval functions that can provide sophisticated analysis to users. - Application development tools: These tools provide the language capabilities that professional information system employees use to build their database applications. Tools include interpreting and compilation tools to CASE (Computer Aided Software Engineering) tools, which automate all the steps of application development and program generation. database application. - Database administration tools: These tools allow database administrators to use personal computers or workstations to perform database administration such as defining databases, executing archives storage or recovery. Back-end software This software includes the Client / Server database software and the network software running on the server as the database server. 5. Distributed database model. Both File-Server and Client / Server models assume that the data resides on a processor and data-access application that resides on another processor, while the database model is dispersed. Assume the database itself is on many different machines.
