Here is a brief outline:
Order updates of any third-party software you have on your machine to insure you have versions that are compatible with V5R1.
Order the latest PTF CUM and appropriate Group PTF for V5R1.
Run the PRTSYSINF command to gather up system documentation for your current release. This can be handy if you need to figure out why something isn't working right after the upgrade.
Apply the latest PTF CUM and appropriate Group PTF patches for the "current" release.
You may want to run a Run a RCLSTG a week or so before the upgrade. This process requires a restrictive state so no other system activity is allowed while this process is running. This is an optional step though.
Just prior to starting the upgrade, do a full system backup (for example: GO SAVE .... Option 21).
Permanently apply all PTF's.
Run option 1. Collect disk space information When that finishes run Option 2. Print disk space information.
Review the report and remove all unneeded data. This will speed up the STROBJCNV process that needs to happen after the upgrade is done.
Delete all unnecessary spool files. This will speed up the spool file conversion process that occurs during the upgrade.
Upgrade to V5R1
Apply latest PTF's
Run the STROBJCNV *ALLUSR *FILE to convert all database files to the new release.
Do another full system backup (For example: GO SAVE .... Option 21)
When I upgraded our system (Model 730 8-way with 1TB of disk), it took about 12 hours, not counting the backups.
This was first published in April 2002