[Koha] Erase or hide all records with itemtype "on order"

Hello, We have a quite big problem in our catalog. Every time we buy books and import records through Z39.50 from national catalog we get like from 2 up to 30 records. All of them have got object attached "on order" automatically. At the moment we have around double the number of records comparing to actual number of items. Is any way to erase them? Is it possible for librarian to do it or must be the IT who can do such a work? Med vänlig hälsning Lukasz Mesek Vuxenbibliotekarie Alingsås bibliotek lukasz.mesek@alingsas.se