If switch is set to -yes then the changes applied by the change_dataitem and change_dataitem_time records (with the same index), will be applied at the discrete time points given in change_dataitem_time. Between those time points, no interpolation is used.
More precise, the change of the data item will be applied directly after the time point has passed.
If you don't specify this change_dataitem_discrete record then interpolation is used.