What is a DSN?
DSN, which stands for data source name, is a method of connecting to a database via ASP (Active Server Page). DSN connections require ODBC, an open standard for API for accessing databases. ODBC handles SQL requests and converts them into requests that the individual database systems understand.
A DSN-less connection is a method of connecting to a database without specifying a named data source. DSN-less connections don’t require the creation of an ODBC DSN. Instead of relying on information stored in a file or in the system registry (as DSN connections do), DSN-less connections specify the driver name and all driver-specific information in the connection string.