Admin Alert: IBM Has Changed the +/- One Release Rule for V5R1 Upgrades

by Joe Hertvik

In a previous column on upgrading OS/400 V5R1 to version V5R3, I stated that the primary partition of an OS/400 machine must be running OS/400 V5R2 in order to support multiple secondary partitions running either OS/400 V5R1 or V5R3 (the +/- one release rule). I was wrong, as I recently learned that IBM had changed the +/- one release rule, enabling you to run an OS/400 V5R3 secondary partition under a V5R1 primary partition.

To refresh your memory, the +/- one release rule means for OS/400 V4R5 and V4R4 (the first two releases to support logical partitioning), the OS/400 release levels of your secondary partitions must be within one release level of your primary partition. So if your primary partition is at OS/400 V4R5, for example, your secondary partitions could run either OS/400 V4R4 (minus one release) or OS/400 V5R1 (plus one release).

For these machines, you could only upgrade an OS/400 secondary partition one release above its primary. This means that, if your machine is running OS/400 V4RX in the primary partition, the following release upgrade constraints are in effect:

• If the primary partition is running OS/400 V4R5, your secondary partitions can only run OS/400 V4R4, V4R5, or V5R1 (+/- one release). Your primary partition cannot support secondary partitions running OS/400 V5R2 or V5R3.
• If the primary partition is running OS/400 V4R4, your secondary partitions can only run OS/400 V4R5 (+ one release), with one exception. If you are running V4R4 on a 6XX, 7XX, or SXX server, a V4R4 controlling partition will also support a secondary partition running V5R1.

The mistake I made was in assuming the +/- one release rule still applies to OS/400 V5R1 as you upgrade to V5R3. It does not, but there are some wrinkles to the new rule. Reader Jeff Huck pointed me in the right direction when he wrote in with the following email:

"You were incorrect in saying that V5R3 cannot be loaded on a system whose primary partition is running V5R1. The +/- one release rule doesn't apply when the primary partition is running V5R1. IBM's V5R3 InfoCenter states that if the primary partition is running OS/400 V5R1, that machine can support secondary partitions running up to the second release after the release the primary partition is running. I've been running an AS/400 720 with the primary partition on V5R1 and the secondary partition on V5R3 without incident for the past several months."

I checked out Jeff's assertion and found out that he was right. IBM has changed the +/- one release rule for some machines with primary partitions running OS/400 V5R1, which can affect an OS/400 V5R1 to V5R3 upgrade. For some of the older models, such as the 6XX and SXX models, the old +/- one rule is still in effect and you may not even be able to load i5/OS V5R3 on your machine at all, depending on your model. But for newer hardware that still has primary partitions at OS/400 V5R1, including the 270, 7XX, 820, 830, and 840 models, there's a new + two/- one release rule, that allows you to run up to four different OS/400 or i5/OS operating systems on the same box, depending on your existing hardware configuration. For systems where the new rule is in effect, here's how it works:

• On some older models--including the older 8XX models as well as the AS/400 720 referenced in Jeff's email--you can run OS/400 V5R1 in the primary partition and OS/400 V4R5, V5R1, V5R2, or V5R3 in the secondary partitions. This satisfies the new + two/- one release rule in that you can run V4R5 (- one release) as well as V5R3 (+ two releases) in secondary partitions where V5R1 is loaded in the primary partition. All of which, in the middle of an OS/400 V5R1 to V5R3 upgrade, allows you to upgrade your secondary systems to V5R3 from an existing V5R1 primary, saving a primary partition upgrade in the process.
• For newer boxes, V5R1 may not be supported at all but IBM is saying that they will support either V5R2 or V5R3 in the primary partitions and up to two future upgrades in the secondary partitions.

To see if your machine is covered under the + two/- one release rule, contact IBM or your business partner. IBM also offers a write-up on logical partition release support for different machines at the IBM Information Center.

The point is that, in spite of my previous statement, you can keep your existing primary partition at OS/400 V5R1 while you upgrade your secondary partition to OS/400 V5R3, which will make V5R1 to V5R3 upgrades much easier in many shops.

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