I was told once by IBM to load your group PTFs firsts (Hiper, DB, etc.) IPL option N, then load the Cume. The IPL...
option will vary depending on when you want to perform said IPL. Unless installing the Cume package is part of an operating system upgrade. In that case, you would want to install the Cume package first, IPL, and then install your group PTFs. I looked back on the installation instructions for the last three V5R2 Cume packages and the instructions reflect the above.
In the latest tip from Glen Bunnell, he is suggesting a different order (based on information received from IBM). Who is right? What is right?
Reading the instructions for V5R3, IBM is telling us to load the Cume, then Hiper, then DB PTF group. We look to the "Experts" to help sort out these confusions. I guess the real tip here is to read the instructions provided by IBM.
The basic problem with making a definitive answer to this question is that the answer is usually "It depends." And if there is a "Right" answer it will probably change with the next release. You are absolutely correct that the real tip is to (always) read the instructions.
First, the reason why someone from IBM might have told you to load group PTF's before the Cume: In a non-upgrade situation generally the group PTF's are updated much more often than the Cume, in the case of the HIPER group weekly vs. three or four times a year for the Cumulative package.
Therefore, the group PTF package is likely to be more current and should include the latest supersedes of the PTF's in the Cumulative package. This might save you a small amount of time in that you wouldn't have to load all of the PTF's and then reload their supersedes. I'm not sure why you would have been told to IPL between loading the group PTF's and the Cumulative PTF's, but in this particular case there could have been a HIPER PTF relating to IPLs or PTF application, for example.
During an upgrade the situation is a little different. Immediately after the upgrade your system is running on the "A" side, with NO PTF's applied. In this example you need to apply the Cumulative package first to ensure your systems stability and then IPL to the "B" side. After the INZSYS completes, you can then load all of the group PTF's required and IPL a second time to apply these.
When a GO PTF option 8 is used to apply a PTF package, the system first determines if you are running on the A side or the B side. If you are running on the A side, the LIC (MF) PTFs are applied immediately. The system is then IPLed to the B side to apply the rest of the PTFs. If you are running on the B side, a mini-IPL is done to the A side to apply the LIC PTFs. The system is then IPLed back to the B side to apply the rest of the PTFs.
Always read the Cumulative/Group PTF Installation instructions, the current Memo to users, and follow the checklist for completing the installation of a new OS/400 release. Occasionally there are special instructions that must be followed exactly to avoid inadvertently running the MAKEAMESS command.