CREATE TABLE TB (
    ID            INT NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH  1 , INCREMENT BY  1 , NO CACHE),
    NAME          VARCHAR( 16 ) NOT NULL,
    REGISTER_DATE TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    ACTIVE_DATE TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        CONSTRAINT ARY_DB_PK PRIMARY KEY ( ID ),
)

CREATE PROCEDURE SESSION_START(IN id INT)
LANGUAGE SQL
SPECIFIC SESSION_START
BEGIN ATOMIC
    DECLARE nTS TIMESTAMP;
    DECLARE SQLSTATE            CHAR( 5 ) DEFAULT '00000';
    DECLARE SQLCODE             INT DEFAULT  0 ;

  
    DECLARE C CURSOR FOR
    	SELECT ACTIVE_DATE TB WHERE ID = id
    	FOR UPDATE OF ACTIVE_DATE
               OPTIMIZE FOR  1  ROW
               WITH CS;

    -- set wait timeout
    SET CURRENT LOCK TIMEOUT WAIT  20 ;
    
    OPEN C;
    -- блокирую доступ к ресурсу
    FETCH C INTO nTS;
    -- некоторые действия
   CLOSE C;
   ..

call SESSION_START( 1 )
блокирует 
call SESSION_START( 2 )