The ESQL/C program and the database server communicate with each other through an interprocess-communication mechanism. The ESQL/C program is the client process in the dialogue because it requests information from the database server. The database server is the server process because it provides information in response to requests from the client. The division of labor between the client and server processes is particularly advantageous in networks where data might not reside on the same computer as the client program that needs it.

When you compile an ESQL/C program, it is automatically equipped to communicate with database servers that reside either on the same computer (local) or over a network on other computers (remote). Figure 12-1 shows a connection between an ESQL/C application and local database servers.

Figure 12-1 ESQL/C Application That Connects to a Local Database Server

Figure 12-2 illustrates an ESQL/C application that connects across a network to a remote database server.

Figure 12-2 ESQL/C Application That Connects to a Remote Database Server

To establish a connection to a database server, your application must take the following actions:

• Identify database server connections that have been defined for the client-server environment of the application
• Execute an SQL statement to connect to a database server