The file level write locks still apply to many filesystems, even the ones which support direct IO. However, some vendors have introducted concurrent direct IO option into their filesystems. Solaris has CIO since some update of Solaris 8. I've used CIO option on AIX 5.2 as well. I haven't heard about CIO for Linux so I guess they don't have it. Also, you have to manually enable concurrent IO in filesystem mount options in order to use it. For Oracle 9.2 on AIX CIO stuff, read this article: http://www-03.ibm.com/servers/aix/whitepapers/db_perf_aix.pdf Tanel. _____ From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of LS Cheng Sent: Monday, September 11, 2006 16:38 To: _oracle_L_list Subject: UNIX file system read/write locks Hi I was wondering if UNIX/Linux filesystem read/write locks still applies in modern filesystems such as qfs/vxfs/OnlineJFS/ext2/ext3? Thanks