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Commands Reference, Volume 1
chvg Command
Purpose
Sets the characteristics of a volume group.
Syntax
chvg [ -s Sync { y | n }] [ -h Hotspare {y | Y | n | r }] [ -a AutoOn {
n | y } ] [ -c | -l ]
[ -L LTGSize ] [ -Q
{ n | y } ] [ -u ] [ -x { n | y } ] [ -S | -R] [ -t [factor ] ] [ -B ] [ -C ] [-g] [ -b { n | y } ] VolumeGroup
Description
The chvg command specifies whether
or not the volume group is automatically activated during the system startup.
If there is a volume group that is infrequently used, you may not want it
activated at system startup because it uses kernel resources (memory).
MAXPVS 32 (128 if -B flag is used)
Note
To use this command,
you must either have root user authority or be a member of the system group.
Because the VGDA space has been increased substantially, every VGDA update
operation (creating a logical volume, changing a logical volume, adding a
physical volume, and so on) might take considerably longer to run.
You can use the Volumes application in Web-based System Manager to change
volume characteristics. You could also use the System Management Interface
Tool (SMIT) smit chvg fast path to run this command.
Note
On AIX 5.2 and later only Enhanced Concurrent Capable volume
groups will be created when the -c or -C flags are specified.
Flags
Notes:
- When changing the characteristics of a volume group that has a snapshot
volume group, the -c, -C, -Q, -l, -x, -b, -t, -L and -s flags are not valid.
- When changing the characteristics of a snapshot volume group the -c, -C, -Q, -l, -x, -b, -t, -L, -s and -h flags are not valid.
-a AutoOn |
Determines if the volume group is automatically activated during
system startup. The AutoOn variable can be either
of the following:
- n
- The volume group is not automatically activated during system startup.
- y
- The volume group is automatically activated during system startup.
|
-b |
Sets the bad-block relocation policy of a volume group.
The default value is yes.
- y
- Will turn on the bad-block relocation policy of a volume group.
- n
- Turns off the bad block relocation policy of a volume group.
|
-B |
Changes the volume group to big vg format. This can accommodate up
to 128 physical volumes and 512 logical volumes.
Notes:
- The -B flag cannot be used if there are any stale
physical partitions or there are any open logical volumes in the volume group.
- Once the volume group is converted, it cannot be imported into AIX 4.3.1 or
lower versions.
- The -B flag cannot be used if the volume group is
varied on in concurrent mode.
- There must be enough free partitions available on each physical volume
for the VGDA expansion for this operation to be successful.
- Since the VGDA resides on the edge of the disk and it requires contiguous
space for expansion, the free partitions are required on the edge of the disk.
If those partitions are allocated for user usage, they will be migrated to
other free partitions on the same disk. The rest of the physical partitions
will be renumbered to reflect the loss of the partitions for VGDA usage. This
will change the mappings of the logical to physical partitions in all the
PVs of this VG. If you have saved the mappings of the LVs for a potential
recovery operation, you should generate the maps again after the completion
of the conversion operation. Also, if the backup of the VG is taken with the
map option and you plan to restore using those maps, the restore operation
may fail since the partition number may no longer exist (due to reduction).
It is recommended that backup is taken before the conversion, and right after
the conversion if the map option is utilized. Since the VGDA space has been
increased substantially, every VGDA update operation (creating an LV, changing
an LV, adding a PV, and so forth) may have a considerably longer duration.
- A big VG only supports Enhanced Concurrent Capable.
|
-c |
Same as -C flag. In AIX 5.2 and later only Enhanced
Concurrent Capable volume groups will be created. |
-C |
Changes the volume group into an Enhanced Concurrent Capable volume
group. Changes the volume group varied on in non-concurrent mode to Enhanced
Concurrent Capable. This requires that the volume group be reimported on all
other nodes prior to activation in Enhanced Concurrent mode. Changes the volume
group varied on in Concurrent mode to an Enhanced Concurrent mode volume group.
Only use the -C flag with the HACMP ES. It has no effect
on volume groups and systems not using the HACMP ES product.
Enhanced Concurrent
volume groups use Group Services. Group Services ships with HACMP ES and must
be configured prior to activating a volume group in this mode.
Use
this flag to change a volume group containing Serial DASD or SSA disks into
an Enhanced Concurrent Capable volume group.
Notes:
- Enhanced Concurrent volume groups use Group Services. Group Services ships
with HACMP ES and must be configured prior to activating a volume group in
this mode.
- Only Enhanced Concurrent Capable volume groups are supported when running
with a 64 bit kernel. Concurrent Capable volume groups are not supported when
running with a 64 bit kernel.
|
-g |
Will examine all the disks in the volume group to see
if they have grown in size. If any disks have grown in size attempt to add
additional PPs to PV. If necessary will determine proper 1016 multiplier and
conversion to bigvg.
Notes:
- The user might be required to execute varyoffvg and
then varyonvg on the volume group for LVM to see the
size change on the disks.
- There is no support for re-sizing while the volume group is activated
in classic or enhanced concurrent mode.
- There is no support for re-sizing for the rootvg.
|
-h Hotspare |
Sets the sparing characteristics for the volume group specified by
the VolumeGroup parameter. Either allows (y) the automatic migration of failed disks, or prohibits (n) the automatic migration of failed disks. This flag has no meaning
for non-mirrored logical volumes
- y
- Enhances the automatic migration of failed disks by permitting one for
one migration of partitions from one failed disk to one spare disk. The
smallest disk in the volume group spare pool that is big enough for one to
one migration will be used.
- Y
- Permits the automatic migration of failed disks and allows migration
to the entire pool of spare disks, as opposed to a one for one migration
of partitions to a spare.
- n
- Prohibits the automatic migration of a failed disk. This is the default
value for a volume group.
- r
- Removes all disks from the Hotspare pool for
the volume group.
Note
This flag is not supported for the concurrent capable
volume groups. |
-l |
Changes the volume group into a Non-Concurrent Capable volume group.
The volume group must be varied on in non-concurrent mode for this command
to take effect. This flag only applies to AIX 4.3 or later. |
-L |
Changes the logical track group size, in number of kilobytes, of the
volume group. The value of the LTGSize parameter
must be 128, 256, 512, or 1024. In addition, it should be less than or equal
to the maximum transfer size of all disks in the volume group. The default
size is 128 kilobytes.
Notes:
- You cannot use the -L flag if the volume group is
varied on in concurrent mode.
- To change the logical track group size, the volume group is varied off
in management mode. This ensures the integrity of the volume group.
|
-Q |
Determines if the volume group is automatically varied off after
losing its quorum of physical volumes. The default value is yes. The change
becomes effective the next time the volume group is activated.
- n
- The volume group stays active until it loses all of its physical volumes.
- y
- The volume group is automatically varied off after losing its quorum
of physical volumes.
Note
Run the bosboot or savebase command
after the chvg -Q n or chvg -Q y command
to update the boot image.
|
-R |
Resumes normal I/O operations for a volume group. |
-s Sync |
Sets the synchronization characteristics for the volume group specified
by the VolumeGroup parameter. Either permits (y) the automatic synchronization of stale partitions or
prohibits (n) the automatic synchronization of stale
partitions. This flag has no meaning for non-mirrored logical volumes.
- y
- Attempts to automatically synchronize stale partitions.
- n
- Prohibits automatic synchronization of stale partitions. This is the
default for a volume group.
Note
This flag is not supported for the concurrent capable
volume groups. |
-S |
Drains I/O's for this volume group and suspends future I/O's. |
-t [factor] |
Changes the limit of the number of physical partitions per physical
volume, specified by factor. factor should be between 1 and 16 for 32 disk volume groups and 1
and 64 for 128 disk volume groups.
If factor is
not supplied, it is set to the lowest value such that the number of physical
partitions of the largest disk in volume group is less than factor x 1016.
If factor is specified,
the maximum number of physical partitions per physical volume for this volume
group changes to factor x 1016.
Notes:
- If the volume group is created in AIX 4.1.2 in violation of 1016
physical partitions per physical volume limit, this flag can be used to convert
the volume group to a supported state. This will ensure proper stale/fresh
marking of partitions.
- factor cannot be changed if there are any stale
physical partitions in the volume group.
- Once volume group is converted, it cannot be imported into AIX 4.3 or
lower versions.
- This flag cannot be used if the volume group is varied on in concurrent
mode.
- The maximum number of physical volumes that can be included in this volume
group will be reduced to (MAXPVS/factor).
- Change of the volume group may require the modification of the LVM meta
data. In this situation the volume group will be varied off in management
mode to ensure the integrity of the Volume group, needing the closure of all
open logical volumes in this volume group. Since logical volumes in rootvg
cannot be closed, rootvg cannot be converted if it needs modification of the
meta-data as part of the chvg -t operation.
|
-u |
Unlocks the volume group. This option is provided if the volume group
is left in a locked state by abnormal termination of another LVM operation
(such as the command core dumping, or the system crashing).
Note
Before using the -u flag, make sure that the volume
group is not being used by another LVM command. |
-x |
Changes the mode which the Concurrent Capable volume group is varied
on. The volume group must be varied on in non-concurrent mode for this command
to take effect.
Note
There is no auto on support for Enhanced Concurrent
Capable volume groups. On AIX 5.2 and later only Enhanced Concurrent Capable
volume groups will be created.
- y
- autovaryon the volume group in concurrent mode.
- n
- autovaryon the volume group in non-concurrent mode.
Note
If the volume group is not created Concurrent Capable,
this command has no effect on the volume group.
In order for this auto-varyon into concurrency of the volume group to take
effect, you must enter the following line into the /etc/inittab file:
rc_clvmv:2:wait:/usr/sbin/clvm_cfg 2>&1
Attention: This entry must be added after the entry used to initiate srcmstr. -- |
Examples
- To cause volume group vg03 to be automatically
activated during system startup, type:
chvg -a y vg03
- To change the volume group vg03 to a supported
state if it is in violation of 1016 physical partitions per physical volume
limit, type:
chvg -t vg03
- To change the maximum number of physical partitions per physical volume
to 2032 and maximum number of physical volumes in volume group vg03 to 16, type:
chvg -t 2 vg03
Files
/usr/sbin |
Directory where the chvg command resides. |
Related Information
Commands: bosboot, lsvg, mkvg, savebase, varyonvg.
The Logical Volume Storage
Overview in AIX 5L Version 5.2 System Management Concepts: Operating System and Devices explains the Logical Volume Manager, physical
volumes, logical volumes, volume groups, organization, ensuring data integrity,
and allocation characteristics.
For information on installing the Web-based System Manager, see Chapter 2: Installation and System Requirements in AIX 5L Version 5.2 Web-based System Manager Administration Guide.
The System Management Interface
Tool (SMIT): Overview in AIX 5L Version 5.2 System Management Concepts: Operating System and Devices explains the structure, main
menus, and tasks that are done with SMIT.
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