The ODBC architecture has four components:
ODBC defines two types of drivers:
One system can contain both types of configurations. The following paragraphs describe single-tier and multiple-tier configurations in more detail.
In a single-tier implementation, the database is
processed directly by the driver. The driver processes SQL
statements and retrieves information from the database. One example
of a single-tier implementation is a driver that manipulates
desktop database systems such as -DBASE, Paradox, Fox Pro
In a multiple-tier configuration, the driver sends SQL requests to a server that processes SQL requests.
The application, driver, and Driver Manager reside on one system, typically called the client. The database and the software that controls access to the database typically reside on another system, typically called the server. This implies that query resolution intelligence resides on the server.
A variant of the multiple-tier configuration is a gateway architecture, where the driver passes SQL requests to a gateway process. The gateway process sends the requests to the data source. The gateway in this scenario can be a piece of hardware or data access software in the form of a low level interface to foreign databases provided by the RDBMS vendor.
The following diagram shows two types of
multiple-tier configurations. From the perspective of an
application, both configurations are identical.