When the citation has been communicated legitimately or the parties have appeared before the judge to pursue the case: 1/ the matter ceases to be res integra; 2/ the case becomes proper to the otherwise competent judge or tribunal before which the action was initiated; 3/ the jurisdiction of a delegated judge is fixed in such a way that it does not cease when the authority of the one delegating expires; 4/ prescription is interrupted unless other provision is made; 5/ the litigation begins to be pending; therefore, the principle while litigation is pending, nothing is to be altered immediately takes effect.
Source: Code of Canon Law (Vatican.va)