There are two primary DSN (data source name) connection types available in a Windows platform: file and machine. A DSN file is a text file that contains all of the relevant connectivity information (including the username and optionally, the password) for the data source and can be easily moved around from machine to machine or deployed with an installation package. A machine DSN stores the connectivity information in the registry, and therefore is specific to only that machine, which may prove much more difficult to setup without direct access to the machine itself.
Access handles links differently depending on which type is chosen. With a file DSN, Access stores the connectivity information in the MDB file and does not need to requery the DSN each time the table is opened. With a machine DSN, Access must query the registry to retrieve the connectivity information with each new connection to the DSN.
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