i found the answer in a another thread - - !
Item maintenance transactions include Item Add, Item Modify, and Item Append.
- Item Add transactions create the GTIN,
- Item Modify transactions write over the entire record of existing GTINs with the included attribute.
- Item Append transactions write over the selected attributes of existing GTINs
I recommend using Item Append for changes to the GTIN. Item Modifies must be used carefully because they write over the entire GTIN. If you had a GTIN that was exported, you would see every attributes populated. If you left a field blank it would write over what was already there, anything already populated has to be left alone so it writes the same information. If you want an attribute changed, you would change that field in the export and it would over write was there.
Item Appends targets only the attribute you want to be changed. Item Modify will overwrite every field in the spreadsheet.
