在Oracle中更新大量行

I have this situation and I'm trying to think of the best way to solve it. I have a database, say DB-A, with a table T-A that has 2 fields - OID and PID. This table has close to 1million rows. Now due to some other issue, the PIDs of most of the rows were incorrectly set to 0 and this was found only after a couple of days.I have this situation and I'm trying to think o