−−There is the so-called single file write lock in unix.
Raw volume/disk does not have this problem.
and solaris/AIX 5.3 now have feature called Concurrent IO, which also
solves this problem.
I am not sure, when we have several dbwr configured, whether different
dbwr will write to the same datafile in the same time.
that is only an issue if you are using a stock filesystem without any database
optimization such as direct IO mount options, Quick IO, Oracle Disk Manager, etc
--
http://www.freelists.org/webpage/oracle-l