Is db2 V9.5 a superset of V9 or are there somethings in each that is not in the other?

V9.5 has everything that 9.1 has and more. However, IBM is still releasing fixpacks for V9.1 in parallel with 9.5, which is something that did not happen with 8.1/8.2.

V9.5 could have been called 10.1 but IBM marketing decided to not charge current 9.1 license holders an upgrade charge for going to 9.5, so it is still the same major version.

The only exception to what I said above is that IBM did change the packaging of the various editions, so that some features that were included for free in 9.1 are extra cost features in 9.5. But some features (like HADR) that cost extra for Workgroup Edition are now included for free. They also renamed DB2 ESE with DPF (data partitioning feature) so that it is now a completely separate edition called DB2 InfoSphere Warehouse.

You're sure? As far as I remember, V8 FixPaks were still released while V9 was already out. So nothing new there.

That is not what I meant. I meant that once 8.2 came out, there were no more 8.1 fixpacks (since V8.1 fixpack 7 was the first release of 8.2).

Notice that for 9.1/9.5 it works differently. Each has their own fixpaks on an independent track (but I don't think there are any features being added in 9.1 fixpacks unless it is already in 9.5).

V8.1 fixpack 7 ** IS ** 8.2 -- that is why 8.1 FP 9 is the same thing as 8.2 FP2 -- very confusing, I hope this never happens again.
There are guidelines as to what warrants a new release versus new version.
Going to 10.1 is a major affair and will not happen because of minor functional enhancement, and, certainly not because of some fixes.
As a rule, a fixpack must never add function - only PTFs (APAR fixes).
Function in 9.5 is a superset of 9.1 , of course.
And 9.1 is a proper and strict subset of 9.5.
Since 9.5 is an independent release (unlike 8.2), fix packs for 9.1 and 9.5 can go in parallel.

Yes, I already said that above. It also worked that way for 7.1 and 7.2 so it could happen again. I don't find it confusing.

The decision to go to a new release (9.1 to 9.5) versus a new version (9.1 to 10.1) is primarily a marketing decision based on whether IBM wants to charge existing customers for the upgrade. 9.5 is a significant upgrade (rewrote almost the entire memory model) with lots of other enhancements, which certainly could be justified as 10.1.

There has not been any such rule for DB2 in the past. They frequently added minor functions in fixpacks. At one time they had odd number fixpacks were fixes only, even number might have some enhancements (or the reverse, I don't recall). I don't know if this is still true.

Yes, I already stated that.

That is exactly I agree with. IBM officially said that it is new release but you know if 9.5 would only be new release 9.1 could be upgraded with fixpacks to become 9.5. So it is new version - like Marcus_A said it could be called 10.1.

But as I have heart new version of DB2 coming soon will be called v9.7 - aren't marketing people funny.

BTW has IBM announced any Dates for COBRA release ?

Yes, you right there. I never considered to be V9.5 and V9.1 comparable to V8.2 and V8.1. That's why I didn't draw this connection.

I tend to ignore major numbers - they are not very meaningful. Personally, I like the idea of some projects to use the date as version number.

Excellent idea! How about DB2 '09, DB2 '10, DB2 '11 ..... similarly to Windows '98 (even Microsoft abandoned that idea)

Won't work. As I have said above: if it is the same version number, then the customer is entitled to upgrade for free. All IBM software works this way and has been this way for thousands of years.

Yes - since the times of Moses

Mazel tov!