FILESYSTEMIO_OPTIONS (AIX 5.2 ML06, 9.2.0.5, JFS2)

How can I confirm that FILESYSTEMIO_OPTIONS is having an effect?

I an on AIX5.2 ML06;
JFS2 filesystems mounted without dio or cio; and Oracle 9.2.0.5. AIO is enabled.

# lsattr -El aio0
autoconfig available STATE to be configured at system restart True

fastpath   enable    State of fast path                       True
kprocprio  39        Server PRIORITY                          True
maxreqs    16384     Maximum number of REQUESTS               True
maxservers 20        MAXIMUM number of servers per cpu        True
minservers 10        MINIMUM number of servers                True

I have trussed DBW0 (and LGWR).

With DISK_ASYNCH_IO = FALSE and FILESYSTEMIO_OPTIONS=SETALL, I see kpwrite calls
With DISK_ASYNCH_IO = FALSE and FILESYSTEMIO_OPTIONS=ASYNCH, I see kpwrite calls.
With DISK_ASYNCH_IO = FALSE and FILESYSTEMIO_OPTIONS=NONE, I see kpwrite calls

With DISK_ASYNCH_IO = TRUE and FILESYSTEMIO_OPTIONS=SETALL, I see listio64 and aio_nwait calls
With DISK_ASYNCH_IO = TRUE and FILESYSTEMIO_OPTIONS=ASYNCH, I see listio64 and aio_nwait calls.
With DISK_ASYNCH_IO = TRUE and FILESYSTEMIO_OPTIONS=NONE, I see listio64 and aio_nwait calls.

I expected to be able to 'turn off' asynch io if DISK_ASYNCH_IO = TRUE and FILESYSTEMIO_OPTIONS=NONE. What have I missed?

This is just a preliminary up to my main question, which is validating that concurrent I/O is also enabled as expected........

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