Data Access and Transactions

“DSN-less” Connections

You can open a connection to a database without creating or specifying a named data source. Connections made in this way are called “DSN-less,” because they don’t require the system administrator to create an ODBC DSN. Rather than relying on information stored in a file or in the system registry, DSN-less connections specify the driver name, and all driver-specific information in the connection string.

Whether or not to use a DSN depends on how much flexibility you want. Connection parameters are readily visible to system administrators. As a result, no matter which connection style you use, there are no extra security benefits. Probably the most common reason for using a DSN-less connection is to connect to a database on a system that is not under your direct control. This makes DSN-less connections good for testing and for applications under development.

The following DSN-less connection strings contain the minimum parameters required by the ODBC drivers of Access and SQL 6.5:

strConAccess = "Driver={Microsoft Access Driver (*.mdb)};DBQ=C:\db.mdb"
strConSQL    = "Driver={SQL Server};Server=(local);UID=sa;PWD="

Essentially, a DSN-less connection is “hard-coded” to use a certain driver, user identity, and network location, which makes it bothersome and difficult to update when the database parameters change. Because the variety of connection parameters can differ greatly from one ODBC data source drive to another, it is recommended that you use a DSN whenever possible.