As a fairly new Administrator to AIX i am a little leary of the OS upgrade I need to do on one of our servers. I have already upgraded the microcode to the lastest level and now need to do the OS. I have the docs and discs from IBM and have determined that I dont want to do a new installation but instead need to do a Migration installation (it is a production box). I know to do a fresh makesysb or 2, and a full backup of the system. but was wondering what pitfalls I should be aware of? What do you use for backup? We current list all files and pipe that list to a backup command. Should we use the smitty backupvg instead? I have searched here for info and have read all pertinant threads, but none addressed 5.1 to 5.2 specifically so I thought I would check. Any hints or other info you can provide would be greatfully accepted.

You said you updated the microcode.
Do you mean the system firmware, or the device microcode?
Some devices like disks, adapters, CD drives, tape drives also have updatable microcode and it is a good idea to make sure all the embedded code is up to date before you attempt a software update / upgrade.

Bear in mind that software tends to be developed on the latest available firmware and microcode and some very strange things can happen if you try to run software on old system firmware or adapter / device microcode it has never been tested on.

http://www14.software.ibm.com/webapp/set2/firmware/gjsn

Also when upgrading to 5.2 I would aim to go straight to a ML of as least 5, higher is better, say 8 or 9.

I updated to the latest system firmware for that machine. I will just be loading whatever level they sent me as a holding point until all the application software has been certified for 5.3 and then i will upgrade to that.

If they send you ML4 or less don't load it. send it back and complain it is too old and therefore unstable to bother with.
Still sheck and update your device (disk, adapter, tape, etc.) microcode before your AIX upgrade. It will make the system much more stable and will save you time in the long run.
A handy tool is the microcode discovery CD, see option 4 in the above link.

According to the disks IBM shipped me they are 5200-09 (dated 9/2006) so i think we are ok in that respect. They also shipped the microcode disk so we have that too. What I really need now is what backup solution should I use?

What machine is it?
A lot of older machines won't support AIX later than 5.1.
The backup solution will depend on what backup devices you have, tape, writeable CD or DVD, a NFS drive, etc.
Local backups are best (unless you have a NIM server) because if the box won't boot you can still boot from the tape / CD / DVD and restore it - You can never be sure your backup solution works until you restore it!
If you can, take 2 mksysbs and a savevg for each vg, just to be safe.
As you are only doing a release not a version upgrade there is little to worry about.
If you have a spare disk or a mirrored rootvg you could investigate alt_disk_install.
http://publibn.boulder.ibm.com/doc_l...I0723971004MKM
Which will allow you to keep your current system and try the upgrade, if the upgrade fails just reboot the original system - still take the backup before you start though...