a: You can't reimport the vg's if you didn't export them. Not sure why hirscha said not to export but to import in his reply.
From the redbook:
Will my machine run the 64-bit kernel?
64-bit hardware is required to run the 64-bit kernel. For AIX 5.2, all IBM eServer pSeries 64-bit hardware can run either the 64-bit kernel or the 32-bit kernel. To verify the processor capability, run the following command:
# /usr/sbin/prtconf -c
The command will return "32" or "64" depending on the capability of the system. If your system does not have the prtconf command, you can use the bootinfo -y command.
In AIX 5.2, the 32-bit kernel is installed by default. The 64-bit kernel, along with JFS2 (enhanced journaled file system), can be enabled at installation time.
If you don't want to reinstall, here's what you do:
Alternatively, after a 32-bit BOS installation operation has finished, manually install the bos.64bit and bos.mp64 filesets from the AIX installation CD.
Can I change back to 32-bit after installing with 64-bit?
Yes, you can change back to 32-bit by booting into service and repointing the symbolic link of unix to unix_mp (32-bit kernel). Perform a bosboot and reboot the partition. For more information about how to do this, refer to the IBM Redbook AIX 5L Differences Guide Version 5.1 Edition Link outside Information Center, section 1.2.3 "64-bit kernel considerations."
(the above should work to change to 64 bit after installing 32 bit as well)
