How to optimize an update SQL that runs on a Oracle table with 700M rows

Question

UPDATE [TABLE] SET [FIELD]=0 WHERE [FIELD] IS NULL

[TABLE] is an Oracle database table with more than 700 million rows. I cancelled the SQL execution a

Answer 1

Are other users are updating the same rows in the table at the same time ?

If so, you could be hitting lots of concurrency issues (waiting for locks) and it may be worth breaking it into smaller transactions.

DECLARE
  v_cnt number := 1;
BEGIN
 WHILE v_cnt > 0 LOOP
   UPDATE [TABLE] SET [FIELD]=0 WHERE [FIELD] IS NULL AND ROWNUM < 50000;
   v_cnt := SQL%ROWCOUNT;
   COMMIT;
 END LOOP;
END;
/

The smaller the ROWNUM limit the less concurrency/locking issues you'll hit, but the more time you'll spend in table scanning.