Main trends of the development to technologies client-server

Work on преодолению defect, organic inherent system fayl-cerver, has brought about appearance more enabling technologies, got name client - a server. Her(its) principle differences are shown on drawing.

file - a server

client - a server

In system client-server processor database takes seats on central server умеете with хранилищем data. He can service simultaneously several клиентских of exhibits, controlling хранилищем and returning inquired information after processing required her(its) local exhibit. To persisting moment possible to name the row a stage, which technology client-server passed in its development: RDА-model, DBS-model and AS-model. In RDA-models клиентское exhibit directs the requests (as a rule, on language SQL) to information resource of the server, on which functions the kernel DBMS. The Kernel processes the got requests and returns the client a result, executed as block data. Under such scheme of the program on computer-клиетах are an initiator manipulate with data, but kernel DBMS is conducted I role. The Main value RDA-models consists in unifications of the interface of the interaction with server by means of standard language request.

The Unification allows to realize the additional measures on protection of prestored information at a rate of tasks of the system of the rights to that go other command. In considered models also occurs the essential unload of the traffic to network to account that that between station of the network are now sent not part of the file database, but commands and answers to them.

The Base DBS-models forms the mechanism of the prestored procedures. The Prestored procedures- programming facility of the server database. They are kept in dictionary database, can divide between different client and are executed on the same computer, where uncared-for programme process of the server database. As a rule, languages, on which the prestored procedures, present itself procedural expansions of the language SQL For the this moment does not exist the united standard for such language facilities; so they are specific for each concrete DBMS. Amongst value DBS-models can be named possibility site администрирования applied function, the most further reduction of the traffic (instead of SQL-request on network are sent calling the prestored procedures), computer resource economy to account of the use one-shot designed a plan of the performing the procedure. To traditional problem, connected with DBS-model, refer to difficulties, accompanying process of the creation, debug and testing the prestored procedures. About popularity and перспективности given models witnesses first of all that she marketed in such broadly used relational DBMS, as Oracle, Sybase, Informix, Ingres.

In AS-models process, executing on computer-client, is identified the client of application (Application Client - А With) and have charge of interface with user. As required execute that or other applied operations he addresses to server of application (Application Server - AS). All operations on information resource are executed special programme component, to which AS plays the role of the client. As example applied component can be named facility of the different types - a database, queue, postal services and others

Itself kernel database Jet, as was it already mentionned earlier, is not a processor, supporting technology client-server. However by means of Access possible to create corresponding to exhibits, linking with client-server source given through ODBC.

The author: Y.N.Antonov Is added: 22.06.2008