Updates with MSDAORA provider for ADO

Hi!
I try to update my recordset over the provider MSDAORA for ADO (used for ORACLE connections).
When the command is executed, the following exception is thrown: 'The operation requested by the application is not supported by the provider.'
When I query the 'Supports' method with parameter 'adUpdate' the result is FALSE.

When I change my application to use a data source with the 'MSDASQL' provider the update works.

Which settings do I need for updating an Recordset with MSDAORA?

Thanks a lot

                  Holger Mueller