As with other transactions, the uncommitted changes of a discrete transaction are not visible to concurrent transactions. For regular transactions, undo information is used to re-create old versions of data for queries that require a consistent view of the data. Because no undo information is generated for discrete transactions, a discrete transaction that starts and completes during a long query can cause the query to receive the  "snapshot too old"  error if the query requests data changed by the discrete transaction. For this reason, you might want to avoid performing queries that access a large subset of a table that is modified by frequent discrete transactions.

declare 
   -- Local variables here
 
  i integer;
begin
   -- Test statements here
 
  dbms_transaction.begin_discrete_transaction;
  SELECT balance_id INTO i from balance WHERE BALANCE_ID= 1 ;   
  UPDATE balance  SET def= 1  WHERE BALANCE_ID= 1 ;  
  DBMS_OUTPUT.put_line('Здесь');  -- тут останавливаемся 
 
  COMMIT;
end;

SELECT * FROM BALANCE_DICT

declare 
   -- Local variables here
 
  i integer;
begin
  SELECT balance_id INTO i from balance WHERE BALANCE_ID= 1 ;   
  DBMS_OUTPUT.put_line('Здесь');  -- тут останавливаемся 
 
  COMMIT;
end;

declare 
   -- Local variables here
 
  i integer;
begin
   -- Test statements here
 
  dbms_transaction.begin_discrete_transaction;
  UPDATE balance  SET def= 1  WHERE BALANCE_ID= 1 ;  
  DBMS_OUTPUT.put_line('Здесь'); 
  COMMIT;
end;