Physical hardware locations will vary on different architectures. For example, if you decide to migrate from a system capable of SMT = 4 (such as POWER7) to one capable of SMT = 8 (such as POWER9), you may see something like the following 'lsdev -Cc processor' output:

#‌ lsdev -Cc processor

proc0 Available 00-00 Processor

proc4 Defined  00-04 Processor

proc8 Available 00-08 Processor

proc12 Defined  00-12 Processor

proc16 Available 00-16 Processor

Like before, you still have the same number of CPUs running. The confusion comes from information in the ODM that was changed when the LPAR was migrated from another frame where there were more physical processors. Essentially, it is a side effect of moving from a processor type that supports four threads per core to one that supports eight threads per core, even though you aren't using all eight threads. As you were previously on a POWER7 system with SMT of 4, an ODM was created with respect to SMT = 4, thus your processors were addressed at every 4 increments; i.e. proc4, proc12.

Now that you have migrated to a POWER9 (a system capable of running SMT = 8), your CPUs are now addressed at every 8 increments, i.e. proc0, proc8, proc16. After a migration, we keep the same ODM and activate only what is required; hence, in addition to your ‘available’ (running) CPUs, the dormant (‘defined’) CPUs were also copied over, but are not running. It simply means that the ODM still contains information about the old system.

You may also see this if you choose to restore from a mksysb.