What is Client/Server Technology in DBMS?

The terms "client" and "server" correspond to roles in a communication by two (or more) software components(like father and son in a family relationship).

Usually the software-component that has the data and the logic of operating on that data is called the server, as it serves with data and activity. A software-component that connects to that server and communicates with it and has not all data and logic is called the client, which is usually quite passive. Server and client are not bound to hardware: You can have a HTTP-server on your working machine as well as a browser (a HTTP-client). In real life you apply separation of concerns also to hardware: You have big data-stores with high responsive hardware that you dedicate to the server-software-component and lots of smaller working machines that have a client-software-component to connect to the servers.

This concept can be applied to most software systems, like databases (server keeps data, client knows how to asks for data), documents (HTTP-servers have the documents, manage them and can even contain logic-components, like PHP scripts or applications, and usually browsers as clients). Server and client are not opposit. Having an application server, like a SAP system, the server is usually also client to other services. The application logic is usually seperated from the database, so the application, being a server for the application clients, is (or has) a client to the database. As the client/server view is a hierarchical division of software communication, you can also have components with equal rights. Some distributed architectures have equal components that communicate with each other, having the same abilities und logic, and eventually having all or part of the data.

In a client-server separation of software both components can be on the same hardware, but they also can communicate via networks and be on different hardwares. Usually the server has the hard-working part so you can have a lot of lightweight clients that only send requests for currently needed data and logic.

But that all is not a must have. When a computer connects to another computer and copies all the logic (programms) and data from it, to become another server, in the process of copying all that information, the taking machine is the client and the giving machine the server.

I'm not sure, what you mean with "file handling systems". A file handling system is usually a software component to serve you data from a file system. Usually it is a local issue, the file system operates on the harddiscs on one hardware. But there are also distributed storages, like NAS (network area storage), where you also have client and server components connected through a network.

So to sum up, what the advantages of a client/server architecture are:

• separation of concerns (this allows for specialisation)
• independent scalability of the server and the clients
• concentration of logic / data that works together (follows separation of concerns) this makes maintainance of the logic on the server much easier (imagine you would have to update all browsers to have a change in your application)