AIX and RAW-device/filesystem

I've recently been informed I'm going to be part of our oracle spport (I'm currently AIX support). I just read the summary about this topic (I'm a latecommer to this news group). The Oracle installation book for AIX makes the two following statements:

1. (pg 5-13) "Under AIX, the use of raw disk devices results in a performance loss of around 25%."
2. (pg 7-15) - I/O is performed directly from the disk to the SGA with little CPU overhead
   • The overhead of AIX read ahead is avoided
   • the overhead of the AIX file system is avoided
   • THe memory overhead of AIX buffer chches . . is avoided

The manual appears to be an older version so is probably not accurate, BUT, I've been puzzling over this contradiction for some time.

Thanks for the summary.

rick:

Richard L. Rhodes       Email:  rhodesr_at_watt.oedison.com               
Ohio Edison Co.         Phone:  216-384-2598