CREATE TABLE RES_LOCK (
    ID_RES       INT NOT NULL, -- Ресурс
    TIME_END     TIMESTAMP,   -- Время жизни блокировки
    LOCK_CONNECT INT DEFAULT CURRENT_CONNECTION
)

create or alter procedure get_lock_res
returns (
    id_res integer,
    time_end timestamp)
AS
declare variable c varchar(1000);
declare variable t timestamp = 'now';
begin
  select ','||conn||',' from get_active_connections into c;

  for select id_res, time_end from res_lock
      where time_end > :t and :c containing ','||:lock_connect||','
  into id_res, time_end do
    suspend;
end

create or alter procedure clear_lock_res (
    id_res integer = null)
AS
declare variable c varchar(10000);
declare variable t timestamp = 'now';
begin
  select ','||conn||',' from get_active_connections into c;

  -- Удаляем неактивные или устаревшие блокировки
  delete from res_lock where time_end < :t or :c not containing ','||lock_connect||',';

  delete from room_lock where id_res = :id_res and lock_connect = current_connection;
end

create or alter procedure set_lock_res (
    id_res integer,
    minutes integer = 15)
AS
declare variable id_item int;
declare variable t timestamp = 'now';
begin
  execute procedure clear_lock_res(:id_res);

  begin
    insert into room_res(id_room, TIME_END)
    values(:id_res, dateadd(:minutes minute to :t));
  when any do
    exception userexception 'Ресурс заблокирован';
  end
end