Client-Server Database Systems

Abstract

Client-server DBMS architectures can be categorized according to the unit of interaction among client and server processes. In general, clients can send data requests to the server as queries or as requests for specific data items. Systems of the former type are referred to as query-shipping systems and those of the latter type are referred to as data-shipping. These two alternatives are shown in Figure 2.1. In query-shipping systems, clients send a query to the server; the server then processes the query and sends the results back to the client. Queries may be sent as plain text (e.g., SQL), in a compiled representation, or as calls to precompiled queries that are stored at the server. In contrast, data-shipping systems perform the bulk of the work of query processing at the clients, and as a result, much more DBMS functionality is placed at the clients (see Figure 2.1). Data-shipping systems can be further categorized as page servers, which interact using physical units of data (e.g., individual pages or groups of pages such as segments), and object servers, which interact using logical units of data (e.g., tuples or objects).¹ In a page server system, the client sends requests for particular database pages to the server. The server returns each requested page (and possibly others) to the client. The client is responsible for mapping between objects and pages. In an object server system, the client requests specific objects from the server; the server is responsible for mapping between objects and pages.

Client-Server is one of the buzziest of the buzzwords. It refers to a computing system that splits much of the workload between PC’s and one or more large computers on a network. Think of it as a restaurant where the waiter takes your order for a hamburger, goes to the kitchen and comes back with some raw meat and a bun. You get to cook the burger at your table and add your favorite condiments. […] It sounds like more work, but it has many advantages: the service is much faster, the food is cooked exactly to your liking, and the giant, expensive stove in the kitchen can be replaced by lots of cheap little grills. Peter H. Lewis New York Times, Sunday, May 2, 1993