Enable 10046 event with level 12.
All the trace files are in the udump dir. You need to sort the trace files and grep p1 (file number) and p2 (block number).

The command is:
$ cd udump
$ grep 'cache buffers chains' ora_*.trc|sed -e 's/.*p1=/ file /' -e 's/ p2=/ block /' -e 's/ p3.*//' | sort | uniq -c |sort -nr|head 5


Tamil