DSNs

Data Source Name (DSN) is a named set of connection parameters used by ODBC-compliant applications to access a data source. A DSN encapsulates the information needed to establish a connection, such as the database driver, server address, database name, and authentication details, so that applications can connect without hardcoding these values.

DSNs can be created and stored in different ways. In Windows, DSNs may be defined as User DSNs (accessible to a single user) or System DSNs (accessible to all users on a machine), and there is also a File DSN, which is a text file containing key-value pairs. The locations differ: Windows DSNs are kept in the registry, while File DSNs are stored as .dsn text files.

Applications request connections by referring to a DSN rather than a set of individual parameters. The ODBC Driver Manager reads the DSN, loads the appropriate driver, and uses the supplied fields (driver, server, database, and optional credentials) to open the connection. Passwords may be stored in the DSN file or managed by the driver, depending on driver and policy.

On Unix-like systems, DSNs are defined in the odbc.ini file, and drivers are described in odbcinst.ini. This convention mirrors Windows in concept but uses plain text configuration files. DSN-less connection strings are also common, where the application provides the driver and connection details directly instead of using a DSN.

DSNs provide portability and centralized management for database connections, but they require careful handling of credentials and permissions, particularly for system-wide DSNs. They are primarily used in the context of ODBC, with similar concepts in other data access technologies.