I have a 32-bit SHARED_MAGIC application that needs to allocate as much
shared memory as it can. I understand the total of all 32-bit shared
memory is limited to 1.75Gb on HP-UX 11.00 (unless I use SHMEM_MAGIC).
Assume I have the shmmax and my swap area big enough to actually allow
allocation of the 1.75Gb.

If I literally allocate as much shared memory as is available (maybe in
multiple segments, to overcome the 1Gb quadrant limit), it will give it
to me, but I gather other 32-bit applications that want to map shared
libraries won't be able to execute. As our application is long-lived,
this would be a problem!

I'm trying to find out the minimum "spare" shared memory the
application should leave on the system to ensure everything *else* can
still run. I can see that this depends on what else I want to run(!),
but if it's just a matter of the usual chatter of shell scripts and
editors and so on, what sort of ballpark are we talking? 10s of Mb? or
100s? More? How could I determine the safe limit?

Cheers,
-nick