RE: New purchase

The big thing when going to 6.1 and beyond is Object Conversion. Read this:
http://www.redbooks.ibm.com/redpapers/pdfs/redp4293.pdf

Upgrading from V5R3 to 6.1 was supported. Technically one should then upgrade from 6.1 to 7.2, then 7.2 to 7.4. Basically IBM only supports upgrading from x-2.
Ideally you upgrade your 520 to 6.1 then to 7.1.
https://www.ibm.com/support/pages/node/6023368
Find some machine (see the above link) which will upgrade from 7.1 to 7.3 then 7.4. Then plop it on your new machine. Most P9's will support 7.2 and above so you could continue the upgrades on the new box. There's a small subset of P9's which support 7.1 (see above link).

If you are going to skip any of these intermediate steps then you're in for a big chance to make a mess. Some may look as this as a good time to start out fresh. Normally they are hobbyists. There's a good chance you'll mess something up. This ain't an AS/400 where you just restore a few libraries, user profiles, etc and you're good to go. Not that it can't be done, but there are a lot of stories out there of people who then spend months cleaning up the mess.

You cannot skip Object Conversion. Read that redbook religiously. If you have old software you're planning on getting rid of you want to dispose of it prior to the upgrade. Their uninstall program likely won't run on anything at 6.1 and above. Again, this ain't an AS/400 where you delete a library and the object owner user profile for that software and you're good to go. They may have hooks throughout the IFS, system directory entries, etc.

However, you may find this interesting reading:
Preparing for the migration from a IBM i model that does not support IBM i 7.4
https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_74/rzamc/rzamcmigrationprep45xx.htm
Again, you still cannot skip Object Conversion. RTF redbook.


Rob Berendt