A boolean indicating if you would like to perform an upsert when an insert operation is used.
Upserts can be used to potentially update an existing record when inserting. NetSuite handles this by using the ExternalId on a given record. If you perform an insert when the ExternalId you specify exists in NetSuite, it will instead update the corresponding record. Otherwise an insert will take place. Set this value to false to always insert new records regardless.