Sorry for my english

I'm working on AIX 4.3.3 with sybase 11.9.2 and recently we have decide to pass the sybase's devices in raw device instead of file system.
When you do that , you can think that the performance will be decreased for 10% but in fact the performance decreased for 40%.

You can measure it for example with a load database onto the two systems.

It seems come from the use of IO kernelized and not of AIO processes to access the data since AIX 4.2.1.

My question is How to tune the system to increase the performances on raw devices with AIX 4.3.3 ?