When an Update or Delete statement is run, the driver locks the records affected by that statement. The locks are released after the driver commits the changes. Under manual commit mode, the locks are held until the application commits the transaction. Under autocommit mode, the locks are held until the statement is run.

When a Select...For Update statement is run, the driver locks a record only when the record is fetched. If the record is updated, the driver holds the lock until the changes are committed. Otherwise, the lock is released when the next record is fetched.