If the disc is scratched contact the librarian responsible for that database as soon as possible. Yes the person will likely have to reboot , and redo the search. Then when displaying skip to beyond the bad reference. Everything locks up during the search process The person may or may not have to reboot . You may have to show the user the print equivalent.
Nothing even loads up.
Unless there is a problem with the software it's a pretty good chance the disc is useless. Offer condolences and show the user the print equivalent. Then contact the selector. Pat dry gently with a paper towel. Any wiping must be done across the tracks - ie from centre to the edge.