Best practice is to add correctly coded MARC records to the catalogue. Correctly coded MARC records will “scope” to your OPAC searches and not to others. You do not need to create item records for these types of resources. Evergreen requires the resource URL and your owning library data in the 856 u,y,z, and 9 MARC tag and subfields. You also need to set the first indicator to 4 and the second indicator to 0. Indicators can not be left blank.
It is quite straightforward to enter the required data in the correct MARC tag as described in the Sitka Training manual at http://docs.libraries.coop/sitka/cataloguing_nonphysical_resources.html