ODBC data sources

An ODBC DSN is a named database connection registered on the hosting server. An application refers to the name, and the connection details live in the DSN rather than in the application’s configuration.

Databases > ODBC DSNs appears when the hosting plan provisions the operating-system resource group and allocates an ODBC quota. Without the quota the item is absent even where databases are present.

When to use one

Mostly for older applications that expect a DSN rather than a connection string — classic ASP, some reporting tools, and line-of-business software written against ODBC.

Modern applications generally take a connection string directly and need no DSN.

Creating a DSN

Each DSN names a driver, the database it points at, and the credentials used to reach it. Once created, the application connects by DSN name alone.

A DSN stores credentials on the server

The database username and password are held in the DSN so the application does not have to supply them. Anyone who can read the DSN configuration on that server can therefore reach the database.

Give a DSN an account scoped to the one database it needs, not a shared or administrative account — this is the standard place an over-privileged database credential ends up.

When a DSN stops working

Check the DSN before the application

Because the connection details sit in the DSN rather than the application, a database password change or a server move breaks every application using that DSN at once while the applications themselves are unchanged.

An application that “suddenly cannot reach the database” after unrelated database work is usually a stale DSN.

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