There are basically two types of ODBC architecture: those that involve multiple tier ODBC drivers and single tier ODBC drivers.
Multiple tier drivers are more common, and are typically used with a remote database server such as Oracle® and SQL Server. Multiple tier ODBC drivers process ODBC calls made by the application, but pass the actual SQL command to the database system.
Single tier drivers, such as the Microsoft® Access® driver, often operate directly on a database file or files. A single tier ODBC driver processes both ODBC calls and the actual SQL commands. In most cases, a configuration using a single tier driver can be contained on just one computer.
