I have a 8.1.7 DB on Solaris 8. This database is constatly loaded by SQL Loader from small files of a few KB to about 15MB. A 11MB file created over a 1GB of redo and SQL Laoder is only loading one table. This table has about ten indexes and the average row size is 63 bytes.
I have examined the log files with Log Miner and over 60% of the log file is filled with "INTERNAL" operations. These operations are taking place on these indexes. The rest of the file is made up of mostly insert and a few deletes.
I have another DB that is 8.1.6 on Solaris 2.6 and it creates very little redo and it is using the same files within SQL Loader. I have not fully examined redo log files from this machine, yet, but what I have seen is night and day.