Hi Michael,
Thank you for you reply,
1) The code D200A200 is fairly 'normal'. It means AIX has been sent a rc.shutdown signal - in HMC terms: delayed shutdown, not operating system shutdown.
How long is that 'normal' process? That time we have waited for about 20 minutes the LED code still D200A200

We can't effort to have a system down more than 30 minutes as it is a production server

For no 2 I will try to check it out
p.s. AIX 5.2 is old, and ML09 is old within AIX 5.2. Check: AIX 5.2 Service Bulletins
Yes sir I know, but our application is not compatible with higher OS level and even higher ML
