AIX 6.1 TL 3 introduced the AIX MPIO driver for the DS4000 storage family, together 
with the command manage_disk_drivers to switch between the drivers.

With AIX 6.1 TL 4 the default device driver for several disk subsystems (DS3000, DS4000, DS5000, and XIV) has changed. The old device drivers (RDAC) is still 
available but the AIX MPIO driver is the default. So if you update a system from an older AIX Version, the RDAC driver will be used. If you install your system with 
AIX 6.1 TL4 the new MPIO driver is the default.

The command manage_disk_drivers displays information about the drivers that manage the storage families, or changes the driver for a family.

With AIX 6.1 TL 4 the usage of the command manage_disk_drivers has changed. Unfortunately the manual page is still the old one.

The new usage is:
# manage_disk_drivers
Usage :
        manage_disk_drivers [-l]
        manage_disk_drivers -d device -o driver_option
        manage_disk_drivers -h

Meaning of the Flags:
-l: Display the Devices, Present Drivers, and Driver Options
-d: The Device to change the Driver
-o: Selects the new Driver
-h: should be help but is interpreted as an illegal option

Examples:
# manage_disk_drivers -l
Device           Present Driver     Driver Options
2810XIV          AIX_AAPCM          AIX_AAPCM,AIX_non_MPIO
DS4100           AIX_APPCM          AIX_APPCM,AIX_fcparray
DS4200           AIX_APPCM          AIX_APPCM,AIX_fcparray
DS4300           AIX_APPCM          AIX_APPCM,AIX_fcparray
DS4500           AIX_APPCM          AIX_APPCM,AIX_fcparray
DS4700           AIX_APPCM          AIX_APPCM,AIX_fcparray
DS4800           AIX_APPCM          AIX_APPCM,AIX_fcparray
DS3950           AIX_APPCM          AIX_APPCM
DS5020           AIX_APPCM          AIX_APPCM
DS5100           AIX_APPCM          AIX_APPCM

# manage_disk_drivers -d DS4300 -o AIX_fcparray

bosboot: Boot image is 42587 512 byte blocks.
 ********************** ATTENTION *************************
  For the change to take effect the system must be rebooted

# manage_disk_drivers -h
manage_disk_drivers: illegal option -- h
Usage :
        manage_disk_drivers [-l]
        manage_disk_drivers -d device -o driver_option
        manage_disk_drivers -h