Update staement in .mnt file when run Dataloader2.dat is not happening

Hello All ,

I had a typical scenario, we have  itm_item.mnt and itm_item_prices.mnt files and put it in to c:/xstore/download  and try to run the dataloader2.dat , it successfully  inserted insert statements in respective item master table

but when come to update statements where it contains price update for a particular list of items are failing and not happenening.

what we need to check  in dataloaderconfig.xml and datasourceconfig.xml files .

Need your valuable suggestions and help to fix this issue.

Thanks,

Ahmed