The following is a list of ODBC concepts and terms you may find helpful while reading this manual.
Client Support – the database client support layer usually contains one or more Dynamic Linked Library (DLL) files in conjunction with configuration files. Database client support is provided by the database vendor. The ODBC driver layer communicates with the client support layer, as illustrated in the first figure. Many database vendors offer TCP/IP network support with their product. The specific files required to communicate using the TCP/IP network protocol is usually part of the client support layer.
Data Source – a data source consists of the data and the information needed to access the data, such as the database management system (DBMS), operating system, and network platform.
Database Layer – the database layer is composed of the database engine and the file or collection of files where the data is actually stored.
Listener Processes – the listener process ties the network protocol to the database engine. This is really the server part of a database server. The first figure shows three separate listener processes to demonstrate one possible configuration serving three separate clients. This layer varies widely depending on database vendors and operating systems.
Network Layer – the network layer is completely separate from the ODBC layers and is specific to the operating system. It is usually provided with the operating system or by a network provider. The client computer and the database server computer each contain this layer.
ODBC Administrator Program– the program used to configure ODBC data sources. Typically installed in the Control Panel, but can also be installed as a separate executable (ODBCAD32.EXE).
ODBC Application – an application that makes ODBC calls. Since the application communicates to the ODBC layer, it is database independent. This means an ODBC application can be written and, by plugging in various ODBC drivers, can access any database. iFIX ODBC is an ODBC application.
ODBC Driver – an ODBC driver translates an ODBC call issued by the application into a specific call(s) for a particular database. In this module, the application links dynamically to a specific database. ODBC drivers are available from a variety of sources. Some companies specialize in writing database drivers. They provide a package that contains over a dozen ODBC drivers for various databases. ODBC drivers are often available from the database vendor as well. Often times, the user has more than one ODBC driver and manufacturer to choose from. The ODBC driver communicates to the client support layer.
ODBC Driver Manager – a module written by Microsoft that is supplied with most ODBC drivers. It acts as the layer between the application and any ODBC drivers. In fact, it loads the driver when the application requests a connection.
NOTE: There is no ODBC software on the database server computer. The ODBC driver on the client translates the ODBC calls into native database calls that the client support layer can understand. Therefore, by the time the database request leaves the client machine, it has been totally transformed into a native call for that database. The listener and engine on the server computer do not know if the request came from an ODBC application or a native database application.
