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DSN vs DSN-less vs UDL: Understanding Database Connection Methods

This article explains the differences between various types of Data Source Names (DSN), DSN-less connections, and Universal Data Links (UDL).

Introduction

DSN stands for Data Source Name. It’s a data structure containing database connection information, essentially what’s needed to connect to a database. The common DSN types are file DSN, system DSN, and user DSN.

UDL stands for Universal Data Link, also known as a Microsoft Data Link. It’s a universal file that contains database connection information.

Different database drivers offer various ways to establish a connection. The following sections describe common techniques used to interact with database providers.

System DSNs

Accessible by anyone with system access.
Storage: Stored in the local machine section of the system registry.
Example: Visible to all users who log into the machine.

User DSNs

Specific to a user on the machine.
Storage: Current user section of the system registry.
Behavior: A User DSN is only visible to the user who created it, not to others logging into the same machine.

File DSNs

Can be stored on disk or on a network.
Usable on any machine that has access to the file.
Storage: Stored in a file, not the registry.
Accessibility: Any user with file access can utilize the File DSN.

UDLs

NI’s (National Instruments’) database toolkit often uses OLE DB to communicate with databases.
With DSNs, commands are translated from OLE DB to ODBC via the OLE DB provider for ODBC.
Recommendation: Using UDLs as the connection method with the toolkit is more efficient (when an OLE DB provider is available for the database).

DSN-less

Doesn’t require a DSN to store connection information.
Storage: Registry, INI file, table, etc.
Mechanism: The user is prompted for connection details at runtime, or the details are retrieved from the storage medium.
Example: SQL Query Analyzer