This came up in another thread: what's the value of the ARG_MAX constant in AIX? And how would you find out if you don't have a C compiler?

Update: shamrock already replied in the other thread:

Still, I'd be interested in knowing what a typical value might be.

This thread has aged somewhat, but as i stumbled over it being interested in ARG_MAX, i feel free trying to plug it.

To my best knowledge it's 24576 on AIX 3, 4 and 5 (on 3.2 I could test this).

Since AIX 5, this limit can be changed at run time with "chdev -l sys0 -a ncargs=number-of-4K-units" [1]. The upper limit is 4MB. getconf is a command
which actually calls sysconf(2) and thus will reflect the run time limit correctly (in contrast to ARG_MAX from the header files).

And with AIX 6, even the default was increased, to 1MB.

This page http://www.in-ulm.de/~mascheck/various/argmax/ with results for various systems gives an idea about existing values among various flavours.

I add links to the AIX documentation, although such deep links are not very stable:
[1] modifying AIX 6 run time limit: IBM Systems Information Center
The page for chdev doesn't contain the very parameter. This page does. The bottom link to "lsdev" then shows the default values.
[2] modifying AIX 5 run time limit (again with links to the related commands) lsdev Command