Hi Marcin Based on the reading I've done around ACFS, I get the impression POSIX locking shouldn't be an issue for Oracle data files. Oracle say you get async and direct I/O on ACFS with fileystem_io_options = SETALL and claim comparable performance to raw devices. I've not come across any discussions of what happens with non-oracle database files and buffered I/O regarding locks though. Hopefully I'll get a chance to put all this to the test at some point… Thanks Austin-- //www.freelists.org/webpage/oracle-l