determine total memory used by Oracle via OS tools

I'm looking for a good way to determine total Oracle memory usage, taking
shared memory into account, using standard Unix/Linux tools.  I can, of
course, easily determine how much memory the database is configured to use,
but need something which indicates how much the OS has actually allocated.
Any suggestions?

Here's a little background.  We recently had an outage on one of our
10.2.0.3 databases running under SunOS 5.10, for which our SysAdmin believes
the root cause to be Oracle using all available virtual memory.  I'm
somewhat skeptical, however, since the problem didn't go away after shutting
down the database (shutdown immediate) and listener...normal operation was
restored only after rebooting the server.  In addition, I've learned that he
used the "prstat -t" command to make this determination, which doesn't
distinguish between shared and non-shared memory (thereby grossly
over-reporting the usage).

At this point we've opened a SR with Oracle to followup on the outage
itself, but I need to be able to provide an alternate (useful) command for
determining memory usage at the OS level next time this sort of thing comes
up.

Thanx!

-- 
"I'm too sexy for my code." - Awk Sed Fred.

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