Dear Manoj
Before deciding to reboot, understand what is running on your AIX system and whether it can withstand a reboot . Are there any applications that need to be stopped before a reboot ? Are there any applications already in a failed state and need fixing before a reboot ? Are there any pending changes that will put the system into a different unexpected state after reboot ?
Then for a successful reboot , you need to fully understand the state of your operating system . Which will give you a list of what to check after a reboot .
For example , you may want to schedule a test reboot before you make multiple updates to verify that the system is operating successfully . Then you can be sure if your updates caused a failure to reboot .
Check your console log for errors reported to identify errors you can ignore or want to fix .
Always create an alt_disk clone as a backup and back out if the updates have unintended results .
Check compatibility of running software with the intended updated AIX level and get confirmation from software vendors .
Examine the current AIX error log for problems that need fixing before a reboot .
Compare your lpar virtualization settings in the profile with the running virtualization settings . These can change if the lpar is stopped and restarted instead of rebooted . Someone could have made changes that only come into effect after a reboot , but they never rebooted .
You should already have a regular job in your environment to capture the system configuration of filesystem and devices configured . Ensure this is upto date to compare after the upgrade . Capture network configurations that could change after an update . Soft NFS mounts that need to be manually mounted . Capture system ODM device customisations that have been tuned for performance that also can change after an update and reset to the default . You will have to ensure these customisations are put back after the update or check if they are no longer appropriate or required.
A fully managed environment will have the scripts and processes in place to check the system before and after reboot .
I hope this helps