>The IBM Support person said he preferred /usr to be below 80%, but my
>question is, "80% of what?".

Not to be a smart alek, but 80% of 100% full: IBM is recommending keeping it
at a level where all those /usr/lpp products can reasonably produce core
files which will fit when created, assuming that such products fail and dump.
Normally /usr is not a dynamic file system like /var, so this is usually not
a concern.  However, various dynamic objects employ /usr/... conventional
Unix names, which should be symlinks into /var, and so if you don't have the
symlinks you can be over-using /usr.  I'd recommend doing housekeeping on
/usr, as it tends to accumulate product install cruft.

You/IBM may be chasing the wrong symptom, though.  The /usr file system level
should only have affected the ability to hold a dump; but what precipitated it?
The ANR7834S tells of a thread responding to an external signal, and you
indicate that it was SIGSEGV.  The cause of that should be pursued.
    Richard Sims, BU