To test/install a new VM level, I'd use a secondlevel VM system, no need to devote an LPAR to it. I still find it easier that one can use the host level VM; the main reasons:: - to provide the network to be able to log on to the second-level VM: -- no access to the HMC required to start it up -- even if TCP/IP in the secondlevel fails, I have access - the secondlevel system can easily get (R/O) access to selected minidisks of the host VM with a simple CP LINK command what enables fixing errors in the seciondlevel, and facilitates preparing put in production.
However, testing Linuxes (or other guests) in a secondlevel VM system, would incur high CPU overhead. I used such a setup the 20 years I spend with my customer, but I didn't have anything else than CMS users, my SW test & installation VM system ran as guest under the main VM production system. It never caused problems. All sysprogs used this test system to install SW. -- Kris Buelens, IBM Belgium, VM customer support
