public static string ExecuteFunction(string Command, string DB)
        {
            string error = "ok";
            string ConnStr = System.Configuration.ConfigurationManager.ConnectionStrings[DB].ConnectionString;
            using (OracleConnection conn = new OracleConnection(ConnStr))
            {
                OracleCommand cmd = conn.CreateCommand();
                cmd.CommandText = Command; //Command = U$MSG_V2_PARAMETERS.SET#USER_NAME(30676)
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.Clear();
                cmd.BindByName = true;
                OracleParameter Response = new OracleParameter("Response", OracleDbType.Varchar2);
                Response.Direction = ParameterDirection.ReturnValue;
                cmd.Parameters.Add(Response);
                conn.Open();
                try
                {
                    cmd.ExecuteNonQuery();
                    error = Response.Value.ToString();
                }
                catch (OracleException e)
                {
                    error = e.Message;
                }
                catch (Exception e)
                {
                    error = e.Message;
                }

            }
            return error;
        }

CREATE OR REPLACE PACKAGE u$msg_v2_parameters
IS
function SET#USER_NAME (
  group_id in INTEGER
) RETURN NVARCHAR2;
END U$MSG_V2_PARAMETERS;

ORA-06550: Строка 1, столбец 15:
PLS-00224: для использов. подобным образом, объект 'U$MSG_V2_PARAMETERS.CLR#USER_NAME' д.б. типа функции или массива
ORA-06550: Строка 1, столбец 7:
PL/SQL: Statement ignored