Source: SMS, Generic Restore Open Mode Values
Explanation: Do not open the data set if it exists on the Target Service.
Nwsm_Do_Not_Overwrite_Data_Set has lower precedence than excluding or including a data set. That is, if a data set is marked as do not overwrite and is also marked as included in the selection list, the data set will be overwritten. To avoid overwriting an included data set, it must be excluded.