In the case of shared memory LPARs, the assigned memory is generally composed of physical memory and memory on paging devices. The memory configured and assigned by desired_mem is then referred to as logical memory, since, similar to the virtual memory in an operating system, it is not only composed of physical memory. Again, the memory is allocated in multiples of the LMB size. The size of the shared memory pool must also be specified in multiples of the LMB size.
However as shown in figure 6.5, there are two important differences in the case of shared memory compared to the allocation in the case of dedicated memory. On the one hand, instead of physical memory, memory can also be assigned from a paging device; on the other hand, physical memory (and paging device memory) are not allocated in multiples of the LMB size, but in units of memory pages (with POWER 4 KB ). So physical memory is assigned to LPARs in smaller units, which very likely provides better utilization.
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