In some of the transactions Data Automator (DA) checks to see whether there is a record or not.
If there is a record DA modifies it rather than a new one. The customer transaction has this function, for example and DA will try and modify the data if it finds one with the same code. A duplicate record will not be created.
Note: We have only added this feature to the transaction types that need it, thus far. As it takes considerable time to add the modify feature, we do this on a case by case example when required.