When DataWindow Designer is connected to an ODBC data source, you might see messages from the ODBC driver that include the words single-tier or multiple-tier. These terms refer to the two types of drivers defined by the ODBC standard.
A single-tier ODBC driver processes both ODBC functions and SQL statements. In other words, a single-tier driver includes the data access software required to manage the data source file and catalog tables. An example of a single-tier ODBC driver is the Microsoft Access driver.
Figure 2-2: Single-tier ODBC driver
A multiple-tier ODBC driver processes ODBC functions, but sends SQL statements to the database engine for processing. Unlike the single-tier driver, a multiple-tier driver does not include the data access software required to manage the data directly.
An example of a multiple-tier ODBC driver is the Sybase SQL Anywhere driver.