OS upgrade is always done from LPAR (Global) except particular case like root WPAR, or version WPAR.

First upgrade the Global LPAR, then use the command syncwpar

syncwpar -A : for all WPAR
sycnwpar wpar1 : only for the wpar1
syncwpar -T wpar1 : for debug mode

First migrate the Global LPAR for example from AIX 6.1 to 7.1.

Then do a syncwpar which will start a migration (using background commands like migwpar, syncroot) on the WPAR from AIX 6.1 to 7.1

If WPAR migration failed In case of partial migration, migration will not return a right exit code, the the WPAR can't be started, except in maintenance mode :

startwpar -m wpar1

If you retry a syncwpar, you have message like:

WPAR is not migratable.
      wpar1 version = 7
      lpar1 version = 7
      

In this case, ERROR WPAR is at same level as Global LPAR, but syncwpar can't be redo, then do:

# mount /wpars/wpar1
# ODMDIR=/wpars/wpar1/etc/objrepos odmdelete -q name=bos.rte -o lpp
# umount /wpars/wpar1
# syncwpar wpar1
# start wpar1