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Open Client Client-Library/C Reference Manual

Chapter 1 Introducing Client-Library

Sybase Client/Server architecture

Sybase Client/Server architecture

Client/server architecture divides the work of computing between "clients" and "servers."

Clients make requests of servers and process the results of those requests. For example, a client application might request data from a database server. Another client application might send a request to an environmental control server to lower the temperature in a room.

Servers respond to requests by returning data or other information to clients, or by taking some action. For example, a database server returns tabular data and information about that data to clients, and an electronic mail server directs incoming mail toward its final destination.

Client/Server architecture has several advantages over traditional program architectures:

• Application size and complexity can be significantly reduced, because common services are handled in a single location, a server. This simplifies client applications, reduces duplicate code, and makes application maintenance easier.

• Client/Server architecture facilitates communication between various applications. Client applications that use dissimilar communications protocols cannot communicate directly, but can communicate through a server that "speaks" both protocols.

• Client/server architecture enables applications to be developed with distinct components, which can be modified or replaced without affecting other parts of the application.

Types of clients

A client is any application that makes requests of a server. Clients include:

• Sybase middleware products such as OmniConnect(TM) and OpenSwitch(TM)

• Standalone utilities provided with Adaptive Server, such as isql and bcp

• Applications written using Open Client libraries

• Java applets and applications written using jConnect(TM) for JDBC(TM)

• Applications written using Embedded SQL(TM)

Types of servers

The Sybase product line includes servers and tools for building servers:

• Adaptive Server is a database server. Adaptive Servers manage information stored in one or more databases.

• Open Server provides the tools and interfaces needed to create a custom server application.

An Open Server application can be any type of server. For example, it can perform specialized calculations, provide access to real-time data or interface with services such as electronic mail. An Open Server application is created individually, using the building blocks provided by Open Server Server-Library.

Adaptive Server and Open Server applications are similar in some ways:

• Both servers respond to client requests.

• Clients communicate with both Adaptive Server and Open Server applications through Open Client products.

But they also differ:

• An application programmer must create an Open Server application, using Server-Library's building blocks and supplying custom code. Adaptive Server is complete and does not require custom code.

• An Open Server application can be any kind of server and can be written to understand any language. Adaptive Server is a database server and understands only Transact-SQL.

• An Open Server application can communicate with non-Sybase protocols, as well as with Sybase applications and servers. Adaptive Server can communicate directly only with Sybase applications and servers; however, Adaptive Server can communicate with non-Sybase applications and servers by using an Open Server gateway application as an intermediary.