I have an application which uses file DSNs to connect to a central database server. This database server is mirrored onto a secondary server, and in the event of a failover, it is my understanding that adding a line in the file DSN "Failover_Partner=" will allow the application to automatically connect to the secondary.

However, this does not appear to work. Below are the contents of my DSNs on the application servers.


DRIVER=SQL Server Native Client 10.0


failover_partner="secondary server"


DATABASE="database name"

APP=Microsoft Open Database Connectivity

SERVER="primary server"

I have tested failing over the databases, and some of our applications which use connections strings with a failover partner specified in their app.config or web.config files are fine. They automatically pick up the secondary server and continue working. They use the same databases and same usernames, so I know it isn't a permissions issue.

The applications that continue to work are on the same subnet as the ones that don't so I know it isn't a network issue.

I can connect to the relevant databases manually in SSMS with the right usernames / passwords.

I am at a loss here. I can't find any reason why this shouldn't work. I can only assume there is something wrong with the DSN, but I don't know what it is, and it only seems to fail when the failover partner needs to be used. When I fire up the app and the primary is available, its fine.

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