When you run lslparmigr -r sys -m <system>, the value of “num_active_migr._supported” shows how many concurrent migrations are possible. For multiple partitions, LPAR names must be comma separated. The maximum number of partition names that can be specified is displayed by the “lslparmigr -r mc -F max_lpars_per_migrlpar_cmd” command.
When trying to migrate multiple LPARs at the same time, the system attempts to migrate them in parallel but only for number of allowed parallel migrations. When you reach the limit of allowed parallel migrations, the next migration will start after one finished, and so on.
The allowed parallel migration is different from one system to another. You can get current value by cli command:
lslparmigr -r sys -m system1
The command will display all partitions migration information for a managed system.
So essentially, if num_active_migr._supported is ‘2’, and you specify six LPAR names on the migration command line, it will run two in parallel until all six have been migrated.