Within reason, I prefer to give the operating system as little memory for file system buffers as possible. The best way to do that is to use raw or direct I/O. Unfortunately, although AIX 4.3 supports file system based direct I/O, Oracle has decided not to use it.

Assuming that my UNIX server only runs Oracle databases, is it better to use the LOCK_SGA parameter or to reduce the size of the UNIX file system buffer cache or use a combination of both ?

I have used both methods on HP-UX with some success but I am now working at an AIX site and the LOCK_SGA parameter is not supported on AIX.

I understand the answer will vary depending on circumstances but I would be interested to know your thoughts on the subject anyway.