problem splitting off a copy of a JFS2 filesystem ...

I'm trying to split off a mirrored copy of a logical volume and mount it as a separate (read-only ) filesystem, as described on the page:

<http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp? topic=/com.ibm.aix.baseadmn/doc/baseadmndita/ HT_baseadmn_snapshotjfs.htm>

... but it isn't working. That page says it should work on AIX 5.2, but here's what I've got:

#> df /s
Filesystem 512-blocks Free %Used Iused %Iused Mounted on
/dev/lv21 209715200 65659248 69% 343096 5% /s

#> lsfs -q /s
Name Nodename Mount Pt VFS Size Options Auto Accounting
/dev/lv21 -- /s jfs2 209715200 rw yes no
(lv size: 209715200, fs size: 209715200, block size: 4096, sparse files: yes, inline log: yes, inline log size: 400, reserved: 0, reserved: 0, DMAPI: no, VIX: no)

#> lslv lv21
LOGICAL VOLUME: lv21 VOLUME GROUP: emcvg
LV IDENTIFIER: 0001dcba00004c00000001047c9fe1c4.5 PERMISSION: read/write
VG STATE: active/complete LV STATE: opened/syncd
TYPE: jfs2 WRITE VERIFY: off
MAX LPs: 512 PP SIZE: 512 megabyte(s)
COPIES: 2 SCHED POLICY: parallel
LPs: 200 PPs: 400
STALE PPs: 0 BB POLICY: relocatable
INTER-POLICY: minimum RELOCATABLE: yes
INTRA-POLICY: middle UPPER BOUND: 128
MOUNT POINT: /s LABEL: /s
MIRROR WRITE CONSISTENCY: on/ACTIVE
EACH LP COPY ON A SEPARATE PV ?: no
Serialize IO ?: NO

#> lsvg -l emcvg | grep lv21
lv21 jfs2 200 400 2 open/syncd /s
#> mkdir /s_copy

#> df /s_copy
Filesystem 512-blocks Free %Used Iused %Iused Mounted on
/dev/hd4 2621440 1475112 44% 3852 1% /
#> chfs -a splitcopy=/s_copy /s

#> echo $?
0

#> df /s_copy
Filesystem 512-blocks Free %Used Iused %Iused Mounted on
/dev/hd4 2621440 1475112 44% 3852 1% /


Note that the "chfs" command returns no error, and exits "0". The split never happens though. Am I missing some crucial but non- obvious step here? This system is at:

#> oslevel -s
5200-09-04

... so I'm fairly up to date. Thanks in advance for the help ... I've never done this before!

-s-

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