[DMWells]

Fred,

This exact situation happened to us when we purchased our first p690 a few years ago. The Technical Architects and Management ignored advice from IBM and their own Technicians (ie me), and built the machine to a budget rather than a specification, allowing only for the memory required by the clients.

Good old Hypervisor hey, the result was that one of the clients didn't have enough memory to run their applications, so after paying all that money for a new server they had to wait until our Department paid to upgrade the memory needed to run the frame itself plus that of the LPAR's.

Another point to remember is that the size of the Hypervisor is calculated and configured, at the time the LPAR is booted, based on the size of the maximum memory figure set in the profile, not the desired figure. So if you use the DLPAR capability of the server to share memory around, you may set the maximum value higher, but if you cross a memory boundry the Hypervisor will grab some more memory for itself, just in case you decide to add more memory to the LPAR later on.

It can be a trap if you don't know about it because you can spend all your time investigating the amount of memory your LPAR's have, rather than the maximum memory they may be given. So it's good to sit down and think about the maximum value and don't just set it to a big size because you might add more memory later.