bosdebug What's the "Backtracking fault log"?

I recently mirrored a rootvg on one of my systems.
After running mirrorvg, I ran bosboot -ad /dev/hdisk1. That seemed OK but
produced a message I've not seen before:
A previous bosdebug command has changed characteristics of
this
boot image. Use bosdebug -L to display what these
changes are.

So I took a look...
bosdebug -L
Memory debugger off
Memory sizes 0
Network memory sizes 0
Kernel debugger off
Real Time Kernel off
Backtracking fault log off

None of that means a lot to me. Comparing with other systems, the only
difference is that the others seem to have "Backtracking fault log on".

I'm running AIX 5.2 ML07. This server is an F50, using the 32-bit kernel.
The ones I've compared it with are p660-6H1s running with the 64-bit kernel
and F80s using the 32-bit kernel. (Also a bunch of others at different
levels of AIX from 4.3.3 to 5.3.) On a quick check, it looks like the 5.1
systems have it turned off and the 5.3 systems have it turned on.

The system seems to be running OK.
The only other thing I did during this activity was to remove an unwanted
paging space from rootvg, (swapoff; rmps). I didn't touch hd6.

Can anybody tell me what this means, and why it might be different on this
system? I've not knowingly run bosdebug before and I doubt that anyone else
has.

--
Simon Green
Altria ITSC Europe s.a.r.l.

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