Each application that you create has its own instance of the tag properties database (Points.mdb). In order that your application is able to share data with this tag properties database, an ODBC data source is required.

Behind the scenes, VTS uses a file DSN (Data Source Name) to connect to an ODBC driver (in the case of most typical VTS applications, the "Microsoft Access Driver") that in turn enables your application to access its tag properties database. In essence, the file DSN acts as a bridge connecting a particular ODBC driver with the data you want to access through that driver.

When you are creating a new standard VTS application, you do not need to concern yourself with establishing a file DSN for it. While each application has its own database files, all applications use a single file DSN to store the connection parameters.