Use this method to navigate the underlying rowset in virtual mode. Although this method is applicable in all modes, it is only necessary in virtual mode. In virtual mode, the underlying DataTable contains only a segment of available data. To navigate the whole rowset, you need to use methods MoveFirst, MoveLast, MoveNext, MovePrevious, Seek. If the rowset contains at least one row, this method moves to the last row and returns True; otherwise, it returns False. After this method, properties Position and CurrentRow point to the first row.

Reference

BaseDataTableSource Class
BaseDataTableSource Members
C1DataTableSource Class
C1ExpressTable Class
Virtual Mode - Dealing with Large Datasets