Release 10.1A: OpenEdge Development:
ADM Reference

RepositionDataSource

Determines whether or not the data-source is to be repositioned on valueChanged of the select. TRUE if the data-source is to be repositioned.

Data type: LOGICAL

Notes:

Read and Write.
This is not needed for the view-as browse option.
This must be set to TRUE if, for example, the data-source also is a data-source for other objects, and those objects need to be refreshed when a value is changed in the combo-box.