Getting pretty off-topic: database systems

James Wilkinson ubuntu at
Sun May 22 23:13:23 UTC 2005

Vincent Trouilliez wrote:
> Had a look at IBM's website. I searched for PL820R and it didn't return
> anything. Already obsolete I guess... or rebadged ? Had a look at their
> current mainframe range, and I can't even see a mention of AIX ! 
> Apparently, they now use some other OS, and they also directly offer
> Linux by themselves, Red Hat or Suse. It really show how hard times are
> now... even the people who can afford million dollar mainframes, try to
> save some money by using Linux instead of a commercial/epxensive Unix !
> Not going to complain, it will only help Linux spread faster :-)

... "now use"?

IBM have four ranges of servers:

The xSeries, which are PC based (Xeon, Opteron and Itanium), running PC
operating systems.

The pSeries, the successors to the RS/6000 line, which run AIX (IBM's
Unix). They're the equivalent of what Bull sells, and run on Power /
PowerPC hardware.

The iSeries, the successors to the AS/400 line of midrange computers.
They run OS/400 (aka i5/OS) with a built-in database. It's a weird and
highly virtual operating system: see
for more details.

And the zSeries, the successors to the S/390 and S/360 mainframes. They
run z/OS and z/VM. The S360s were the 1960s mainframes that built IBM's
computing reputation. Modern mainframes are very different beasts to
their forebears and to smaller computers: they tend to be
ultra-reliable, able to spot hardware failures, work around, and swap
out dodgy hardware without affecting user programs. They also have the
ability (now coming to other computers) to run lots of "instances" of
operating systems in parallel.

IBM offer Linux on all of them. But running Linux on a mainframe doesn't
just make it a very big and expensive PC. You still get all the
reliability, and all the ability to run thousands of instances of
operating systems independently. You can "consolidate" thousands of PC
servers onto one mainframe, each server's tasks being adopted by one
Linux instance. So it looks to software and to end users like it's
lots of computers. But it's still only one computer: it's a lot cheaper
to administer and look after than hundreds of individual servers.

And that means that for a lot of companies, an IBM mainframe is the
cheapest way of running a lot of Linux instances. They want to run Linux
because Linux has the applications they want to run and z/OS doesn't
(although you can run that in another partition).

It's turned IBM's mainframe division around, and has been making IBM a
lot of money.


E-mail address: james | We still have enough spare cardboard sitting around  | to send a bus by Parcelforce, although not enough
                      | wrapping to be sure they wouldn't deliver it broken
                      | into two pieces.  -- Alan Cox

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