IY94343: MKLV -TO ON BIG VOLUME GROUPS FAILS

netyu

In any case, it should not hurt anything. Depending on how Oracle is configured, you may require it (if Oracle must write starting at byte 0).
However, if oracle, or another application is AIX savvy, and uses an ioctl call to determine the setting, or you setup an application to skip over the first 4k bytes (actually I need to lookup the actual size of the LVCB these days) you should not need it.
Remember also, setting the volume group to scalable also makes it a null operation.
-T O
            For big vg format volume groups, the -T O option indicates that the logical
            volume control block will not occupy the first block of the logical volume.
            Therefore, the space is available for application data. Applications can
            identify this type of logical volume with the IOC INFO ioctl. The logical
            volume has a device subtype of DS_LVZ. A logical volume created without this
            option has a device subtype of DS_LV. This option is ignored for old and
            scalable vg format volume groups.



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IY94343: MKLV -TO ON BIG VOLUME GROUPS FAILS TO PUT SOME LV INFORMATION APPLIES TO AIX 5300-07

APAR status
Closed as program error.
Error description When creating a logical volume with device subtype of
DS_LVZ,
using the '-TO' flag, lslv reports 'DEVICESUBTYPE :
DS_LVZ'.
The problem shows up only after the following:
a subsequent chlv command or any LVM command that can
update VGDA on disk or a reboot, lslv reports
'DEVICESUBTYPE : DS_LV' instead of the correct device
subtype of 'DS_LVZ'.
Local fix
Problem summary ****************************************************************
* USERS AFFECTED:
* Users of BIG volume groups with the bos.rte.lvm fileset at
* the 5.3.0.53 or 5.3.0.54 level.
****************************************************************
* PROBLEM DESCRIPTION:
* When creating a logical volume with a device type of DS_LVZ
* using the '-TO' flag, lslv reports a DEVICESUBTYPE of DS_LV
* rather than DS_LVZ.  The problem shows up only after a reboot
* or any subsequent chlv or other LVM command that can update
* the VGDA on disk.
* This problem can cause some applications, such as Oracle, to
* fail to start, and could result in database corruption.
****************************************************************
* RECOMMENDATION:
* Install APAR IY94343.
* Prior to the fix for IY94343 being available an interim fix
* may be downloaded from:
* ftp://ftp.software.ibm.com/aix/efixes/iy94343/
****************************************************************
Problem conclusion Ensure that the subtype information is written to disk.
Temporary fix *********
* HIPER *
*********
Comments 5200-10 - use AIX APAR
IY94347
5300-06 - use AIX APAR IY94343
5300-07 - use AIX APAR IY94343
APAR information
APAR number
IY94343
Reported component name
AIX 5.3
Reported component ID
5765G0300
Reported release
530
Status
CLOSED PER
PE
YesPE
HIPER
YesHIPER
Submitted date
2007-02-01
Closed date
2007-02-21
Last modified date
2008-02-14
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
IY94347
Publications Referenced
Fix information
Fixed component name
AIX 5.3
Fixed component ID
5765G0300
Applicable component levels
R530 PSY U810462
   UP07/05/24 I 1000 ®
PTF to Fileset Mapping
U810462
bos.rte.lvm
5.3.0.55

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IY90895: MKLV -T AND -O FLAG OPERATION FIXED APPLIES TO AIX 5300-07


A fix is available
Obtain fix for this APAR

APAR status
Closed as program error.
Error description mklv command sets the device subtype (DEVICESUBTYPE) on
a logical volume (LV) created in a Regular Volume
Group (VG).
On regular VG:
mklv -TO -y lvtoset vg00 1
lvtoset
> lslv lvtoset | grep DEVICESUBTYPE
DEVICESUBTYPE : DS_LVZ
According to LVM docuemtation the -TO parameter is
ignored on LVs created on Regular VGs and SVGs.
This is seen at AIX 5.2 ML9 and is also on AIX 5.3 ML5.
Also, when the -T flag is used, any values supplied by the
-o flag are ignored.
Local fix Workaround is to not issue the mklv -TO flag on creating
LVs on regular VGs.
Also, use the "chlv -o Y lvname" command to change
non-serialized LVs to serialized LVs if desired.
Problem summary Some applications, such as Oracle, will see the device
subtype is DS_LVZ and overwrite the LVCB that is stored in the
first 512 bytes of the logical volume.  This will cause some
logical volume commands, such as extendlv, to output warning
messsages ("Warning, cannot write lv control block data.").
However, no functional problems will result from this.
If an application requires LV serialization and is running
on an LV that does not have serialization enabled, then
overlapping I/Os will be scheduled in parallel instead of
serially.  This could cause problems with applications which
require LV serialization.
Problem conclusion Update mklv so that it ignores the -T flag for regular volume
groups, matching the documented behavior, and process the -o
flag regardless of whether or not the -T flag is present.
Temporary fix Comments 5200-10 - use AIX APAR
IY90893
5300-06 - use AIX APAR IY90895
5300-07 - use AIX APAR IY90895
APAR information
APAR number
IY90895
Reported component name
AIX 5.3
Reported component ID
5765G0300
Reported release
530
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Submitted date
2006-10-19
Closed date
2006-10-23
Last modified date
2008-09-20
APAR is sysrouted FROM one or more of the following:
IY90893
APAR is sysrouted TO one or more of the following:
Publications Referenced
Fix information
Fixed component name
AIX 5.3
Fixed component ID
5765G0300
Applicable component levels
R530 PSY U809509
   UP06/12/08 I 1000
PTF to Fileset Mapping
U809509
bos.rte.lvm
5.3.0.53

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