Reset-Grid
When set to 1, the Grid control is completely emptied.
When set to 2, the Grid control is emptied except for the headings. If row headings are present, the Grid cells are emptied but not physically removed from the control.
When set to 3, the Grid control is emptied except for the column headings. Row headings, if present, are removed.
The search panel shown on top of the column headings, if present, is always removed.
 
Example - Modify a grid to reset all its rows but the column heading rows
procedure division.
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  modify screen-1-gr-1 reset-grid 3
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