vgchange(1M)															      vgchange(1M)

NAME

       vgchange - set LVM volume group availability

SYNOPSIS

   Activate volume group
       availability quorum]
	      resync_daemon_count] [vg_name...]

   Set volume group high-availability cluster attributes
       cluster sharable] vg_name

   Change activation mode of sharable volume group
       availability {vg_name...}

   Quiesce an active volume group
       quiesce_mode quiesce_time] vg_name

   Resume a quiesced volume group
       vg_name

   Remarks
       Serviceguard cluster operations require the installation of the optional Serviceguard software, which is not included in the standard HP-UX
       operating system.

       Mirrored disk operations require the installation of the optional HP MirrorDisk/UX software, which is not included in  the  standard  HP-UX
       operating system.

       If  a  combination  of  volume  groups version 1.0 and 2.0 or higher arguments are supplied, then the arguments may not be processed in the
       order they are listed on the command line.

DESCRIPTION

       The command with the option activates or deactivates one or more volume groups.

       For volume groups that are used in a high availability cluster, when the option is specified together with the option, the  command  allows
       cross-activation,  changing the activation mode of an active sharable volume group directly to the specified activation mode, without first
       having to deactivate the volume group.

       The command with the specifies whether the indicated volume group(s) can be used in a high availability cluster, optionally the option  can
       also be specified to configure whether the volume group is sharable (or is for exclusive activation only).

       The  command  without  the  resync_daemon_count option (default) will spawn one nomwcsyncd process for each volume group containing logical
       volumes, and this can degrade system performance when many of these volume groups are activated at the same time.  The  resync_daemon_count
       option  provides a way to control the number of concurrent nomwcsyncd processes spawned.  This parameter is advisory, LVM may use a differ-
       ent value internally as necessary.

       The option allows quiescing an active volume group to facilitate creating a consistent disk snapshot copy of all the  physical  volumes	in
       the  volume  group.   Metadata on the physical volumes is brought current and remains unchanged until normal operation is resumed using the
       option (or when the optionally specified quiesce_time time has expired).  Specifying when quiescing the volume group  quiesces  application
       reads  and  writes  to  the  volume group.  This mode is suitable for most situations.  Specifying when quiescing the volume group quiesces
       application writes to the volume group while allowing reads to proceed as usual.  This mode provides improved access to the data when  used
       with  applications  that  are capable of quiescing updates while allowing queries.  See the section for a more complete description of qui-
       esced volume groups.

       vg_name must be defined as a volume group in the file or If vg_name is omitted, all volume groups defined in and are affected, except  when
       the or options are specified.  Only a single volume group can be provided with these options.

   High Availability Cluster Overview
       Volume  groups  can  be defined on disk volumes that are accessible by more than one system in a high availability cluster.  This situation
       has a high potential for data corruption unless higher level cluster software services are used to coordinate shared  access  to  the  same
       volume group by all systems.

       A  volume  group  can  be  marked as part of a cluster.	When such a group is activated in exclusive mode, it can be accessed for exclusive
       read-write activity by only one of the systems at a time; the other systems can have read-only access to the data.  When the  volume  group
       is also marked as sharable, it may be activated in shared mode for read-write access by all the nodes in the cluster.

       The  configuration  of a shared volume group can be changed only if it is activated in exclusive mode.  Cross-activation between shared and
       exclusive modes of shared volume groups is possible with the option to

       Simultaneously quiescing a volume group on all the systems sharing the volume group can be accomplished by invoking with  the  option  from
       any  node  in  the cluster.  A Serviceguard cluster-lock volume group cannot be quiesced, because initializing or updating the cluster-lock
       requires writing to the disk.

   Options and Arguments
       recognizes the following options and arguments:

	      vg_name		The path name of a volume group.

	      Set volume group availability.
				availability can have one of the following values:

				Activate each specified volume group
				       and all associated physical and logical volumes for read-write access.

				       If a volume group is marked as part of a high availability cluster, it is activated in exclusive read-write
				       mode, as for the option.

				Activate each specified volume group
				       and  all associated physical and logical volumes for exclusive read-write access.  The volume group must be
				       marked as part of a high availability cluster, and the availability software must be running on the system;
				       otherwise, the volume group is not activated.

				       With  the  option,  the activation mode of a shared volume group is changed to exclusive.  The volume group
				       will remain active during the operation.  The operation will not be performed if the volume group is active
				       in more than one node, or if it is not currently in shared mode.

				Activate each specified volume group and all associated
				       physical  and  logical  volume  for shared read-write access.  The volume group must be marked as part of a
				       high availability cluster and marked sharable; otherwise, the volume group is not activated.

				       Please note HP MirrorDisk/UX software is only supported in a clustered environment with a  maximum  of  two
				       nodes  configured  for  volume  group  version 1.0 and 2.0. For volume group version 2.1 or higher, HP Mir-
				       rorDisk/UX software is supported in a clustered environment with a maximum of sixteen nodes configured.

				       With the option, the activation mode of a shared volume group is changed to shared.  The volume group  will
				       remain active during the operation.  The operation will only be performed if the current activation mode of
				       the volume group is exclusive.

				If the or option is executed on a currently active volume group, without the option, attempts to include any phys-
				ical  volumes  that  were previously listed as missing.  This is useful if a physical volume has come back online.
				However, no automatic synchronization of any mirrored logical volumes is done.	If  synchronization  is  required,
				execute the command (see vgsync(1M)).

				Activate each specified volume group
				       and  all associated physical and logical volumes for read-only access.  This option is ignored for a volume
				       group that is already activated.

				       If a volume group is marked as part of a high availability cluster, the high availability software must	be
				       running on the system; otherwise, the volume group is not activated.

				Deactivate each specified volume group
				       and  its  associated  logical  volumes.	You must close the logical volumes prior to executing this option.
				       For example, if the logical volume contains a file system, the file system must be unmounted.

	      Control the membership of volume groups in a high availability cluster.
				cluster can have one of the following values:

				Mark each specified volume group as a member of a high availability cluster.
				       The high availability software must be running; otherwise, the volume group is not  marked.   Needs  to	be
				       done on one node only.  may be optionally specified with the option to indicate whether the VG is sharable,
				       and when the option is used without the VG is marked not sharable.

				Remove each specified volume group from membership in the high availability
				       cluster.  The high availability software does not have to be running to perform this operation.

				The volume group must be deactivated with the option before a option can be executed.

	      Force deactivation of each specified volume group
				and its associated logical volumes while a sync is in progress.

				This option requires the deactivation option, otherwise an error will be returned.

				This option is only valid for high availability clusters.

	      Disable the opening of logical volumes that belong to each specified volume group.
				If the option is set, later attempts to open the logical volumes will fail.  To allow an opening of these  logical
				volumes to succeed, execute

	      Activate each specified volume group only if all of the physical volumes
				that belong to it are available.

	      Set the quorum enforcement for each specified volume group.
				quorum can have one of the following values:

				Enforce the quorum requirement.
				       This is the default.

				Ignore the quorum requirement.

				The  option can be used to activate the volume group when the disk quorum is not maintained because too many disks
				were lost.  Since it ensures the integrity of the LVM configuration information, it is normally not  advisable	to
				override the quorum.

	      Disable the synchronization of stale physical extents
				within the volume group specified by vg_name.  This option is only effective when used with the or option.

	      Automatically resume normal read/write access to the volume group
				once  the  specified  quiesce_time  (in  seconds) has expired.	This option should be used when quiescing a volume
				group that contains critical resources (e.g., root or swap logical volume) that are necessary for normal operation
				of  the  system,  or other circumstances where manually executing the may not be possible once the volume group is
				quiesced.  The quiesce_time can be any value from 1 to 2^31-1.	This option is	only  valid  when  used  with  the
				option.

	      Cross-activate a active sharable volume group, changing the activation mode
				to  the specified activation mode.  This option is only valid when used with the availability option.  Cross-acti-
				vation can only be used to change the activation mode from shared mode to exclusive mode, or from  exclusive  mode
				to shared mode.

	      specify the advisory count to control the number of
				nomwcsyncd  threads  spawned for processing when activating the volume group(s).  Specifying a resync_daemon_count
				of causes a reasonable number of threads to be spawned (currently defined to be 4).

	      Quiesce an active volume group to guarantee that
				the LVM metadata is consistent.  This allows a system administrator to perform a snapshot of all the disks in  the
				volume group.  The volume group remains quiesced until it is resumed again using the option or automatically after
				the optionally specified quiesce_time (given using the option) has expired.  See the section for a  more  complete
				description of quiesced volume groups.	The quiesce_mode can have one of the following values:

				Quiesce both reads and writes to the volume group.

				Quiesce writes to the volume group.
				       Applications may open and read from logical volumes belonging to the volume group.

	      Resume a previously quiesced volume group.
				I/O  that  was	quiesced is allowed to complete.  LVM commands and resync operations are enabled.  See the section
				for a more complete description of quiesced volume groups.

	      Control the sharability of volume groups in a high availability cluster.
				sharable can have one of the following values:

				Mark each specified volume group as sharable.
				       The high availability software must be running; otherwise, the volume group is not marked.  This  only  has
				       to be done from one node of the cluster.

				Remove the shared attribute from the volume group.
				       The high availability software does not have to be running to perform this operation.

				The volume group must be deactivated with the option before a option can be executed.

	      Activate each specified volume group using multiple parallel threads.
				Physical  volumes  will  be  attached  to  the volume group using threads. If the option is not specified with the
				option, logical volumes of the volume group will also be synchronized using threads.  Activation  will	be  serial
				across volume groups and logical volumes belonging to different volume groups will be synchronized serially.

				The maximum number of threads used can be controlled using the system tunable.

				NOTE: With this option, the selection of primary path and ordering of alternate links may vary across volume group
				activations.

   Mirrored Disk Activation
       When the optional HP MirrorDisk/UX software is running and a volume group is activated,	LVM  performs  the  necessary  mirror  consistency
       recovery for each logical volume in the volume group based on the state of Mirror Write Cache and Mirror Consistency Recovery (see the Con-
       sistency Recovery section of lvdisplay(1M)).  In a non-shared environment, LVM supports and the recovery.  Logical volumes in 1.0  and  2.0
       volume group versions, activated in shared mode, do not support for mirror consistency recovery.

	      Recover mirror consistency
			by using the Mirror Write Cache and Mirror Consistency Record.	This mode implies that the Mirror Write Cache is on.

	      Recover mirror consistency
			by searching all logical extents and copying data from a non-stale copy to all the other mirror copies.  This mode implies
			that the Mirror Write Cache is off.

	      Do not recover mirror consistency during volume group activation
			on this logical volume following a system crash.  This mode implies that the Mirror Write Cache is off.

       Once mirror consistency is recovered using the configured policy, the mirrors are resynchronized (any stale extents made current) by  copy-
       ing data from a non-stale copy to the stale mirror copies.  If the option is specified on the command line, mirror synchronization does not
       occur.  However, for those logical volumes that have Mirror Write Cache turned off, mirror synchronization is done independently of whether
       the option appears on the command line.

   General Activation
       If cannot access a physical volume, it lists the volume's status as missing.  If too many physical volumes in the volume group are missing,
       reports that the group does not have a quorum and cannot be activated.  The lack of a quorum can be overridden with the option.

   Quiesced Volume Groups
       A quiesced volume group presents a stable and consistent disk image suitable for creating snapshot copies of the disks in the volume group.

       Quiesced volume groups have the following characteristics:

	      o  The physical volumes in the volume group appear as though the logical volumes were closed and the volume group  was  deactivated.
		 They  remain  unchanged until the command is issued to resume access to the VG or until the optionally specified quiesce_time has
		 expired.

	      o  When is specified, reads and writes are queued until the volume group is resumed.  When is specified, reads proceed as usual, but
		 writes are queued until the volume group is resumed.  In the latter case, reading from the volume group will return the last data
		 written before the volume group was quiesced.

	      o  LVM display commands are allowed to proceed as usual.

	      o  LVM mirror resynchronization and configuration commands are rejected.

	      o  I/O that is queued because a volume group is quiesced will not be completed until after the volume group is  resumed,	regardless
		 of  any  logical  volume  I/O	timeout that is set on the LVs.  Some applications may be sensitive to this delay and could report
		 errors or warnings as a result.

EXTERNAL INFLUENCES

   Environment Variables
       determines the language in which messages are displayed.

       If is not specified or is null, it defaults to "C" (see lang(5)).

       If any internationalization variable contains an invalid setting, all internationalization variables default to "C" (see environ(5)).

EXAMPLES

       Activate volume group

       Deactivate volume group

       Forced deactivation of volume group

       Activate volume group using multiple parallel threads:

       Activate volume group without synchronizing extents that are not current on logical volumes that have Mirror Write Cache turned on:

   Exclusive Activation
       Set up volume group for use in a high availability cluster:

       Activate all volume groups;  activate those that are marked for membership in a high availability cluster in shared mode:

       Activate all volumes that are marked for membership in a high availability cluster in exclusive mode:

   Cross Activation
       Set up volume group for use in a high availability cluster.

       To make configuration changes, to a volume group activated in shared mode, deactivate the volume group by executing the	following  command
       on each cluster node except one:

       On the single node, where the volume group is active:

   Quiescing a Volume Group
       Quiesce LVM metadata writes and application reads and writes to volume group

       Quiesce LVM metadata and application writes but allow application reads to volume group

       Resume normal reads and writes to volume group (after having quiesced them earlier) :

       Quiesce volume group quiescing both reads and writes and automatically resume normal read/write access in 600 seconds:

WARNINGS

   Ordinary Operation
       In  ordinary operation (that is, without the optional high availability software), it is possible to activate a volume group for read-write
       access from more than one physically connected system, leading to a high potential for data corruption.	Therefore, if  access  is  desired
       from  more  than one system to a single volume group, it is important that only one system activate the volume group for read-write access;
       the other systems can use read-only access.  There is no problem if all systems activate the volume group for read-only access.

       Furthermore, volume group information is only read from the disks during volume group activation.  Dynamic changes to the volume group such
       as the following are not propagated to other systems sharing the volume group:

	      Logical volume configuration changes.

	      Changes to the status of the mirrored extents.

	      Bad-block relocation that occurs during write operations.

       Because	of  these  limitations,  when sharing volume groups between systems it is recommended that logical volumes be accessed only by one
       system at a time.  If logical volumes must be accessed simultaneously, the logical volumes should not be mirrored and should not have  bad-
       block relocation turned on, or all systems should use read-only access to the logical volumes.

SEE ALSO

       mount(1M), vgcreate(1M), vgdisplay(1M), vgextend(1M), vgreduce(1M).

       If Serviceguard is installed: cmcheckconf(1M), cmquerycl(1M), and

																      vgchange(1M)