The bank account of the dead person ceases to exist. What happens to iban status after that? 'Invalid' and unavailable (when i'm checking the number)?
When someone dies, then their bank account does not get terminated immediately. First the bank does actually need to get notified of the death, which in many countries does not happen automatically. Then control over the account is transferred to the estate of the deceased, which can then decide what to do with it (keep using it or terminating it).
When an account gets terminated (for whatever reason), then the IBAN becomes invalid. Any attempt to wire money to the account or to direct-debit the account will be rejected.
However, a bank can later reissue an IBAN number after an account was terminated. I know that because I actually had to write a program once to terminate long unused IBAN numbers in a bookkeeping system. A wire transfer got to a wrong person, because they got a reused IBAN number from a very old business partner of our client. But banks usually wait a couple years before they do that to avoid any trouble from misrouted wire transfers or direct debits. One bank told us that they block previously used account numbers for 5 years. But I am not sure if this is more or less than the industry standard. I would assume that banks with fewer customers or which don't yet exist for long have enough account numbers left that there is no need for them to reuse old ones.