RBS will be used in either case. Alter the target table to NOLOGGING, and this will not generate any redo during the inserts. When done, change it back to LOGGING. Commit regularly so that the RBS won't grow too big.
I think its because of the RBS. Check to see if there are any frequent log switches over say 30 min to 1hr while the inserts are taking place. You are not quite using the redo log files in actual terms. Don't worry about LGWR being active.
Yes, changes to the RBS tablespace are just like any other (more or less). They are logged to your redo log files.
By dedicating a couple of devices to your redo logs, you can minimize the impact of LGWR. If your LGWR is spinning all the time, you may want to check to see if LGWR is checkpointing too much (Checkpoint not complete message in alert.log) or you may need to tune your redo activity.
you can only use nologging option if you do direct inserts
first alter the table to nologging attribute
insert /*+ append */ into xxxx
select * from yyyy;
This wont generate redo log
direct insert is insert.... select....
there is no way you can avoid logging in a normal insertion, only in a direct insert.
And there is no way you can avoid using RBS... as far as I know.
Just to add some note, if you do direct inserts you will start inserting after High Water Mark because of APPEND hint, however APPEND is required for direct inserts. This will work better if you are doing it to a temporary truncated table