It is possible to share an IFL between multiple LPARs as long as all the LPARs involved are ONLY IFLs. You can't mix and match.
A second-level test system is more than sufficient, though, and you can have more than one to do training for multiple groups in parallel w/o huge hassles. > Is it possible to create LPARs in an IFL so I can run > multiple z/VM, one for test and one for production?
