There is something that does not seem quite right here. You say that you retrieve StartDate and EndDate, but your sample query only has two columns.

Your error message barfs about column 3 and says that it is called Notetext?

Also, dbo seems like a funny name for a schema in an Oracle database.

But all apart from that, what happens is this: First SQL Server wants to compile the batch, so it queries the OLE DB provider about the columns returned by the query, and the OLE DB provider reports that this particular column is nullable. However, when you actually run the query the provider says that the column is nullable, and SQL Server does not appreciate this joke.

This kind of situation is very difficult to troubleshoot, since it requires knowledge about both SQL Server and Oracle. Although, I would hold Oracle and the OLE DB provider as the prime suspect. I would make sure that you have the latest version of the provider, and that it matches the version of Oracle you are connecting to.