Take a look at the figures for logical I/O in the raw trace files. You may find that the number of LIOs per update increases steadily as the apply processes works through the batch. If so, the statistic that stands out will probably be "consistent gets - examination" - which will be a large fraction of the "consistent gets".
Regards
Jonathan Lewis http://www.oracle.com/technology/community/oracle_ace/ace1.html#lewis
The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html
Cost Based Oracle: Fundamentals http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html
Oh, also, the Applier process was driving one CPU to 100% (4-cpu box). Only one Applier process was used. Interestingly, when I tested with 10 batches of 100,000 rows each, two Applier processes were used. Don't know why. I guess that as Log Miner worked its way through the archived logs, each time that it got through one batch and started another one, there were probably two streams available for SQL Apply to work on. Guessing...
Mark -- //www.freelists.org/webpage/oracle-l
-- //www.freelists.org/webpage/oracle-l