Data source name

In computing, a data source name (DSN, sometimes known as a database source name though data sources are not limited to databases) are data structures used to describe a connection to a data source. Most commonly used in reference to ODBC, DSNs may also be defined for JDBC and other data access mechanisms.

DSN attributes may include, but are not limited to:

• name of the data source
• directory of the data source
• name of a driver which can access the data source
• user ID for data access (if required)
• user password for data access (if required)

The system administrator of a client machine creates a separate DSN for each relevant data source.

Standardizing DSNs offers a level of indirection that various applications (for example: Apache/PHP and IIS/ASP) can take advantage of in accessing shared data sources.

Types of data source name

Two kinds of DSN exist:

• Machine DSNs - stored in collective configuration files (e.g., /etc/odbc.ini, ~/.odbc.ini) and/or system resources (e.g., Windows Registry HKLM\Software\ODBC\odbc.ini)
• File DSNs - stored in the filesystem with one DSN per file

These are further broken down into

• System DSNs - accessible by any and all processes and users of the system, stored in a centralized location (e.g., /etc/odbc.ini, /etc/odbc_file_dsns/<filename>)
• User DSNs - accessible only by the user who created the DSN, stored in a user-specific location (e.g., ~/.odbc.ini, ~/odbc_file_dsns/<filename>)

Misuse of the term

The term DSN is sometimes mistakenly used in place of connection string. A connection string typically fully describes a data source, while a DSN typically relies on some external system resources and/or configuration file.

Example of use

Software (e.g., Crystal Reports, Microsoft Excel, PHP, Perl, Python, Ruby) users can submit CRUD (Create, Read, Update, Delete) queries to a data source by establishing a connection to the DSN.

might look like the following:

Dim DatabaseObject1
Set DatabaseObject1 = Server.CreateObject("ADODB.Connection")
DatabaseObject1.Open("DSN=DSNname;")

In PHP using the PEAR::DB package to open a connection without an external DSN (a "DSN-less connection", i.e., using a Connection String), the code might resemble the following

require_once("DB.php");
//$dsn = "<driver>://<username>:<password>@<host>:<port>/<database>";
$dsn = "mysql://john:pass@localhost:port/my_db";
$db = DB::connect($dsn);

See also

• ADO.NET
• JDBC
• ODBC
• OLE DB