deleteAllRows() is used to remove all the rows of a DISPLAY ARRAY or INPUT ARRAY list:
CALL dlg.deleteAllRows("screen array")
There is some specifics about using variables with ui.Dialog methods.
You can learn about them here.
One shouldn’t include deleteAllRows() to BEFORE ROW, AFTER ROW, BEFORE DELETE, AFTER DELETE, BEFORE INSERT, AFTER INSERT control blocks. However, the method is allowed in an ON ACTION block.
The method needs only one argument which specifies the name of the screen array the list of which should be deleted.
During the DISPLAY ARRAY or INPUT ARRAY statement execution, the dialog automatically appends a temporary row to the list after deleteAllRows() deletes all the rows. The temporary row won’t be added if the AUTO APPEND = FALSE attribute is used. In this case, the current row register will be changed in order to prevent it from being greater than the total number of rows.
The BEFORE ROW control block is executed if deleteAllRows() deletes the currently selected row during execution of an DISPLAY ARRAY or INPUT ARRAY statements which have the focus.