The Committee usually convenes at least once a year at a plenary session ("plenum"), and functions as a top forum for discussion about relevant policy issues. The Committee operates, however, on the principle of democratic centralism; i.e., once a decision is made, the entire body speaks with one voice. The role of the Central Committee has varied throughout history. While it generally exercises power through formal procedures defined in the party constitution, the ability for it to affect outcomes of national-level personnel decisions is limited, as that function has generally been, in practice, carried out by the Politburo and retired party elders who retain influence. Nonetheless, Central Committee plenums function as venues whereby policy is discussed, fine-tuned, and publicly released in the form of "resolutions" or "decisions".