Cursor with commits? - Updates 33 millions rows fills the UNDO

The simple query below updates 33 millions rows, but terminates after filling my undo.  What is the best way to batch this update with commits and a cursor.   I appreciate your help. 

update productview set CUSTOMER_ID = 'value2' where CUSTOMER_ID = 'none';

I just tried the code below but received error ORA-01002 fetch out of sequence:

declare
i number := 0;
cursor s1 is select * from test_productview where customer_id = 'none' FOR UPDATE;
begin
for c1 in s1 loop
update test_productview set CUSTOMER_ID = 'value2'
where current of s1;

i := i + 1; -- Commit after every X records
if i > 1000 then