WRITE_NOS will not overwrite data objects in external storage. If a WRITE_NOS operation encounters an object with the exact path and name it is trying to write, it will stop and generate an error.
In this case, the WRITE_NOS operation will stop, return an error, and will not create a manifest file, even if the MANIFESTFILE option was used. The write operation may have written some data objects to the external storage location, and these must be removed manually before attempting to repeat the same WRITE_NOS operation. For information on how to determine the data objects that must be removed from external storage before repeating the same WRITE_NOS operation, see Teradata Vantage™ - Native Object Store Getting Started Guide, B035-1214.