This is the reply I got from Support:
I haven't tried yet... i will try it out the both methods,
the one which is posted above in this thread (simpler version) and the support
I would suggest you to do the following.
1) rmdev -Rdl every "Defined" fcs adapters
2) make the client lpars paths to vio1 defined (rmdev -dl vscsiX)
If you have lpars with disk mapped as LVs, then you will have
to consider stopping the lpars having those VTDS...
3) shutdown vio1
4) create a copy of the vio1 lpar profile with NO vhost slots
at the HMC, let's name it "NO_VHOST".
5) Start VIO server with this 'NO_VHOST' profile
Since there is no vhost, we will not configure the vhosts,
nor the VTDs, hence not open the hdisks.
6) You should now be able to rmdev all the DS4K hdisks, since
no VTDs are active.
7) Reboot the VIO server with (keeps the NO_VHOST profile)
8) Verify you have "IBM MPIO DS4700 Array Disk" disks
change the reserve_policy according to the value needed
9) You may reboot once more, to check that values are kept
Across reboot.
10) Shutdown the server, and, boot it from the "Default" profile
11) Enable the client path again (cfgmgr).
