I understand that the crucial part of the proces of certification is looking up the reference transactions accordingly to certification keys in CCV. And it is done when a locally accepted (in terms of integrity) transaction is broadcasted to the whole cluster so that the other nodes may accept it or not. But after a reference transaction is certified by the whole cluster, does every node delete it from its local CCV? Do the nodes that’ve certified the transaction, wait for positive/negative reply from other nodes? If not, how do other transactions get certified positively if they modify the same row, e. g., a day later?