How unknown values are handled during sorts varies depending on the type of data source. If one of the components of your scrolling index is unknown and the data source does not provide a consistent sort order for unknown values, you can force scrolling by using the USE–INDEX phrase with another index whose unique components do not include the unknown value. See your data-source documentation for information on how your data source handles unknown values during sorts.

The ODBC DataServer performs data retrieval against a data source that will allow records in its result sets that have null values in any of its index components. To prevent records in result sets that have null values in their index components, use the OpenEdge startup switch -znnic when you start your OpenEdge client.