DECLARE
existing_program NUMBER;
BEGIN
SELECT count(*) INTO existing_program
FROM ALL_SCHEDULER_PROGRAMS WHERE PROGRAM_NAME = 'prog_name' AND OWNER='owner';
IF existing_program = 1 THEN
dbms_scheduler.DROP_PROGRAM(PROGRAM_NAME => 'prog_name');
END IF;
END;
/
BEGIN DBMS_SCHEDULER.create_program(program_name => 'owner.prog_name', ...); END;