CVM allocates internal resources only as needed. However, this would not work for virtual space, as a re-allocation might change the address. Hence, all shared space is pre-allocated. This has no effect, other than using up swap space.
Not quite, but close. AIX's MPI is run on top of POE, so you use poe commands. Once your environmental variables are set up correctly (and the .hostfile, instead of .cvmrc), you can run sor w/ four procs as:
sor -procs 4 -- -s
sor -- -n4 -s
The command line is executed from the first machine in the .cvmrc for the UDP version, but whether the MPI version is executed from the first line in the .hostfile or from a gateway machine depends on the way your machines are set up. Ask your staff about POE.