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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:
  1. 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.
  2. 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:
  1. The -B flag cannot be used if there are any stale physical partitions or there are any open logical volumes in the volume group.
  2. Once the volume group is converted, it cannot be imported into AIX 4.3.1 or lower versions.
  3. The -B flag cannot be used if the volume group is varied on in concurrent mode.
  4. There must be enough free partitions available on each physical volume for the VGDA expansion for this operation to be successful.
  5. 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.
  6. 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:
  1. 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.
  2. 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:
  1. 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.
  2. There is no support for re-sizing while the volume group is activated in classic or enhanced concurrent mode.
  3. 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:
  1. You cannot use the -L flag if the volume group is varied on in concurrent mode.
  2. 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:
  1. 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.
  2. factor cannot be changed if there are any stale physical partitions in the volume group.
  3. Once volume group is converted, it cannot be imported into AIX 4.3 or lower versions.
  4. This flag cannot be used if the volume group is varied on in concurrent mode.
  5. The maximum number of physical volumes that can be included in this volume group will be reduced to (MAXPVS/factor).
  6. 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

  1. To cause volume group vg03 to be automatically activated during system startup, type:
    chvg -a y vg03
  2. 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
  3. 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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