The primary benefit of using direct I/O on a unix system is using less memory. Direct I/O bypasses buffer cache which is dynamic on the most of modern Unix (and Unix-like systems, for Linux fans) systems. If you have never had any problems with memory, you're unlikely to see any benefits. You can even notice a slowdown for the jobs that are mainly read-only because by using direct I/O, you eliminated the file system prefetch and caching effects. If your database has 1,000 online users, you definitely do want direct I/O, or each and every process will cache its small part of DB files in both kernel memory (buffer cache) and SGA. -- Mladen Gogala A & E TV Network Ext. 1216 > -----Original Message----- > From: Nuno Souto [mailto:nsouto@xxxxxxxxxxxxxx] > Sent: Tuesday, October 26, 2004 7:18 AM > To: Oracle-L@Freelists. Org (E-mail) > Subject: Re: Direct I/O, better performance? > > > Roger, I wouldn't discount direct I/O completely. > Try it on redo log files. > The other thing you should be aware is that the standard > file system does a lot of work that you have to compensate > for when you start replacing its functionality. Readahead > on sequential operations is one obvious one. -- //www.freelists.org/webpage/oracle-l