SQL & PL/SQL

Hello,

We need to update 2 columns on a very large table (20000000 records). Every row in the table is to be updated and the client wants to be able to update the records by year. Below the procedure that has been developed

DECLARE
l_year VARCHAR2 (4) := '2008';

CURSOR c_1 (l_year1 VARCHAR2)
IS
SELECT ROWID l_rowid, (SELECT tmp.new_code_x
FROM new_mapping_code_x tmp
WHERE tmp.old_code_x = l.code_x) code_x,
(SELECT tmp.new_code_x
FROM new_mapping_code_x tmp
WHERE tmp.old_code_x = l.code_x_ori) code_x_ori
FROM tableX l
WHERE TO_CHAR (created_date, 'YYYY') = l_year1;

TYPE typec1 IS TABLE OF c_1%ROWTYPE
INDEX BY PLS_INTEGER;

l_c1 typec1;
BEGIN
DBMS_OUTPUT.put_line ( 'Update start - '
|| TO_CHAR (SYSDATE, 'DD/MM/YYYY HH24:MI:SS')
);

OPEN c_1 (l_year);

LOOP
FETCH c_1
BULK COLLECT INTO l_c1 LIMIT 100000;

EXIT WHEN l_c1.COUNT = 0;

FOR indx IN 1 .. l_c1.COUNT
LOOP
UPDATE tableX
SET code_x = NVL (l_c1 (indx).code_x, code_x),
code_x_ori =
NVL (l_c1 (indx).code_x_ori, code_x_ori)
WHERE ROWID = l_c1 (indx).l_rowid;
END LOOP;
COMMIT;
END LOOP;

CLOSE c_1;

DBMS_OUTPUT.put_line ( 'Update end - '
|| TO_CHAR (SYSDATE, 'DD/MM/YYYY HH24:MI:SS')
);
END;
/

We do not want to do a single update by year as we fear the update might fail with for example rollback segment error.
It seems to me the above developed is not the most efficient one. Any comments on the above or anyone having a better solution?

Thanks