I’ve been working on a ClickOnce application that uses Oracle. It seems to work fine for most people, but not for one user – he gets an ORA-12539 TNS Buffer Under or Over Flow message. What’s weird is he only gets it when he uses the ClickOnce app.

The Oracle support site just says: contact support in the explanation for that error message.

So I did some digging around to try and find out why *I* wasn’t getting the error. I turned on client tracing and fired it up. This time I get the error. It turns out the act of tracing seems to add an entry to the connection string. Because ClickOnce apps live nice and deep in the directory tree this causes the connection string to overflow. D’oh!

Fingers crossed, problem is solved by turning off tracing.