OS/400 PASE Is Not Dead

by Timothy Prickett Morgan

My apologies to the IBMers and the folks at OS/400 shops whose blood pressure shot up last week after I said that IBM had apparently withdrawn support for the OS/400 Portable Applications Solution Environment, or PASE, AIX runtime environment. This is not what IBM meant to convey in its product announcements from the week earlier, and if I had stopped to think for more than one second about it, I would have remembered that withdrawing PASE is impossible.

There are reasons for my stupidity--including a high fever and the beginning of a flu and working under a tight deadline on a Friday, which is never a good combination--but there simply is no excuse for not having thought through what I actually wrote down when I read IBM's poorly written announcement. They are always written poorly, and after 16 years of reading these things, I know better than to take something like this at face value. Again, I plead temporary viral insanity. (The error was in "Old i5 520 Express, iSeries Upgrades, and OS/400 V5R2 Booted".)

The good news is, IBM is not withdrawing PASE, which is an AIX runtime environment that is woven into OS/400. The reason why IBM is not withdrawing PASE is simple: The third-generation TCP/IP stack IBM created for OS/400 is actually the TCP/IP stack from AIX running inside PASE. Moreover, Tivoli Storage Manager and a bunch of other programs, like the OpenSSH shell, run inside PASE. If IBM removed PASE, it would have to either port these things to OS/400 natively using C++ compilers or run them on AIX partitions. The former is not a good option because the C compiler for OS/400 is not as well regarded as the one for AIX, and the latter is not good because it would require all OS/400 servers to have an AIX partition if they wanted to use TCP/IP--and they most certainly all do.

Here's a statement from George Timms, the lead developer of PASE for IBM Rochester, which sheds some light on IBM's current and future plans for PASE:

"i5/OS PASE has not been withdrawn. i5/OS PASE runtime was originally a priced feature of OS/400, but became a no-charge part of the operating system in V5R2. i5/OS PASE runtime is strategic to i5/OS and will continue to be maintained and enhanced on the eSeries i5. There are no plans (or even discussion of plans) to change this.

Increasing numbers of applications, as well as significant portions of i5/OS itself, rely on the PASE runtime. PASE continues to be enhanced to support the most current released version of AIX available at the i5/OS general availability--for the current i5/OS release V5R3 PASE is based on AIX 5L Version 5.2.

The PASE runtime often provides an i5/OS application developer with the best application portability to other UNIX platforms. And because PASE uses the underlying i5/OS support for configuration, user IDs, file systems, authorization, auditing, and so forth, PASE avoids all of the complexity of managing a separate AIX or Linux partition."

What IBM actually did do, by the way, was remove the option of getting PASE as a separately orderable feature for older versions of OS/400. It is automatically packaged with OS/400 V5R2 and i5/OS V5R3.