APPEND into tables

By using the APPEND hint, you ensure that Oracle always grabs "fresh" data blocks by raising the high-water-mark for the table. If you are doing parallel insert DML, the Append mode is the default and you don't need to specify an APPEND hint. Also, putting the table into NOLOGGING mode will allow Oracle to avoid almost all redo logging.

insert /*+ append */ into customer select (. . .) from customer_xx;