This command is very similar to DEL: it removes the specified keys. Just like DEL a key is ignored if it does not exist. However the command performs the actual memory reclaiming in a different thread, so it is not blocking, while DEL is. This is where the command name comes from: the command just unlinks the keys from the keyspace. The actual removal will happen later asynchronously.
Integer reply: The number of keys that were unlinked.
"OK"redis> SET key2 "World"
"OK"redis> UNLINK key1 key2 key3
ERR Unknown or disabled command 'UNLINK'