lvchange(1M)															      lvchange(1M)

NAME

       lvchange - change LVM logical volume characteristics

SYNOPSIS

       availability] autobackup] mirror_consistency] contiguous] schedule] distributed] mirror_write_cache] permission] relocate] strict] IO_time-
	      out] lv_path

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

DESCRIPTION

       The  command  changes  certain  characteristics of a logical volume.  Other characteristics can be changed with the and commands (see lvex-
       tend(1M) and lvreduce(1M)).

       The command-line options specify the type and extent of change.	Each current characteristic for a logical volume remains in  effect  until
       explicitly  changed  by the corresponding option.  All options take effect immediately, except which takes effect only when new extents are
       allocated by the command.

       If a logical volume is striped, its scheduling policy is always parallel and its allocation policy  is  always  strict  and  noncontiguous;
       these attributes cannot be changed with

       The  command  can also be used to change the timeout value for a logical volume.  This can be useful to control how long an IO request will
       be retried (for a transient error, like a device timeout), before giving up and declaring a pending IO to be failed. The  default  behavior
       is  for	the  system  to  continue to retry an IO for a transient error until the IO can complete. Thus, the IO will not be returned to the
       caller until the IO can complete. By setting a non-zero IO timeout value, this will set the maximum length of time  that  the  system  will
       retry  an  IO.  If the IO cannot complete before the length of time specified by the IO timeout, then the IO will be returned to the caller
       with an error. The actual duration of the IO request may exceed the logical volume's maximum IO timeout value when the underlying  physical
       volume(s) have timeouts which either exceed the logical volume's timeout value or are not an integer multiple of the logical volume's time-
       out value (see pvchange(1M) for details on how to change the IO timeout value on a physical volume).

   Options and Arguments
       The and options are meaningful only if the optional HP MirrorDisk/UX software has been installed on the system.

       recognizes the following options and arguments:
	      lv_path The block device path name of a logical volume.

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

		     Make a logical volume available.
			    An open of the logical volume will succeed.

		     Make a logical volume temporarily unavailable.
			    An open of the logical volume will fail.  However, all current processes that have	the  logical  volume  open  remain
			    open.

	      Set automatic backup for this invocation of this command.
		     autobackup can have one of the following values:

		     Automatically back up configuration changes made to the logical volume.
			    This is the default.

			    After  this  command executes, the command (see vgcfgbackup(1M)) is executed for the volume group to which the logical
			    volume belongs.

		     Do not back up configuration changes this time.

	      Set mirror consistency recovery.
		     This option is effective only when is specified or previously set.  mirror_consistency can have one of the following values:

		     Set mirror consistency recovery on.
			    LVM achieves mirror consistency during volume group activation by going through all logical extents and  copying  data
			    from a nonstale copy to the other mirror copies.

		     Set mirror consistency recovery off.
			    LVM does not perform mirror consistency recovery on this logical volume when the volume group is activated following a
			    system crash.  This setting should only be used on logical volumes that do not require mirror consistency recovery	or
			    where  mirror  consistency	recovery  is  performed by another subsystem; for example, swap.  See the section for more
			    details.

	      Set the contiguous allocation policy.
		     contiguous can have one of the following values:

		     Set a contiguous allocation policy.
			    Physical extents are allocated in ascending order without any gap between adjacent extents and all	extents  are  con-
			    tained in a single physical volume.

		     Do not set a contiguous allocation policy.

		     A	nonempty  logical  volume  that  has a noncontiguous allocation policy cannot be changed to a contiguous allocation policy
		     unless it happens to meet all the requirements of the contiguous allocation policy.  See lvcreate(1M)  for  more  information
		     about the contiguous allocation policy.

	      Set the scheduling policy when a logical extent
		     with  more than one mirror is written.  (The scheduling policy of a striped logical volume is striped and cannot be changed.)
		     schedule can have one of the following values:

		     Establish a parallel scheduling policy.

		     Establish a sequential scheduling policy.
			    Use this value with care, because it leads to performance loss in most cases.

	      Change the distributed allocation policy.
		     distributed can have one of the following values:

		     Turn on distributed allocation.

		     Turn off distributed allocation.

		     Force distributed allocation to be on.

		     When the distributed allocation policy is turned on, only one free extent is allocated from the first available physical vol-
		     ume.   The  next  free  extent  is allocated from the next available physical volume.  Allocation of free extents proceeds in
		     round-robin order on the list of available physical volumes.

		     When the distributed allocation policy is turned off, all available free extents are allocated from each  available  physical
		     volume before proceeding to the next available physical volume.

		     The distributed allocation policy REQUIRES the PVG-strict allocation policy ( ) to ensure that mirrors of distributed extents
		     do not overlap (for maximum availability).

		     The distributed allocation policy is incompatible with the striped scheduling policy ( ) and the contiguous allocation policy
		     ( ).

		     See lvcreate(1M) for more information on the distributed allocation policy.

		     The  option will fail if the existing logical volume has any two consecutive logical extents on the same physical volume.	To
		     override this failure, use the option.

		     If a logical volume with the distributed allocation policy has at least two consecutive logical extents on the same  physical
		     volume, then lvdisplay(1M) will display the allocation as (vs.

		     See lvdisplay(1M) for display values.

	      Set the Mirror Write Cache flag.
		     This option is allowed only when the logical volume is not opened.  mirror_write_cache can have one of the following values:

		     Set Mirror Write Cache on.
			    Every  write  to a mirror copy is recorded in the Mirror Write Cache and written into the Mirror Consistency Record on
			    the disk if a cache-miss occurs.  This allows LVM to determine whether all mirror copies are  identical,  even  across
			    system  crashes.   When the volume group is activated, the Mirror Consistency Record is used to perform mirror consis-
			    tency recovery.

		     Set Mirror Write Cache off.
			    Mirror write does not incur an additional write to the Mirror Consistency Record on the disk.

	      Set the access permission.
		     permission can have one of the following values:

		     Set the access permission to read-write.

		     Set the access permission to read-only.

	      This parameter is valid for volume group version 1.0 only.
		     For volume group versions 2.0 or higher, it is ignored and relocation is never supported.

		     Set the logical volume bad block relocation policy.  This is an obsolete flag available only to  provide  compatibility  with
		     prior HP-UX releases.  The relocate flag can have one of the following values:

		     This release does not provide the LVM bad block relocation feature;
			    but  for  compatibility reasons, the value is maintained as a logical volume attribute.  Displaying the logical volume
			    attributes will show the value of the flag selected.  However, regardless of the selection, no new relocations will be
			    done.

			    If	the  volume  group  is	activated on a different HP-UX release that provides the bad block relocation feature, bad
			    blocks may be relocated depending upon the value of this flag.  Although no new relocations  will  be  done,  any  bad
			    block relocations present on a logical volume (activated on HP-UX releases that provided this feature) will be honored
			    when the volume group is activated on this HP-UX release.

			    is the default value of this flag.

	      Set the strict allocation policy.
		     Mirror copies of a logical extent can be allocated to share or not share the same physical volume or physical  volume  group.
		     This  option  only makes sense when the physical volumes of the volume group that owns the specified logical volume reside on
		     different physical disks.	strict can have one of the following values:

		     Set a strict allocation policy.
			    Mirrors of a logical extent cannot share the same physical volume.

		     Set a PVG-strict allocation policy.
			    Mirrors of a logical extent cannot share the same physical volume group.

		     Do not set a strict or a PVG-strict allocation policy.
			    Mirrors of a logical extent can share the same physical volume.

		     When a logical volume is mirrored, the following changes are not allowed:

		     o	From nonstrict to strict
		     o	From nonstrict to PVG-strict
		     o	From strict to PVG-strict

	      Set the
		     IO_timeout for the logical volume to the number of seconds indicated. This value will be used to determine how long  to  wait
		     for  IO requests to complete before concluding that an IO request cannot be completed. An IO_timeout value of zero(0) causes
		     the system to use the default value of "forever".	NOTE: The actual duration of the request may exceed the specified IO_time-
		     out  value  when the underlying physical volume(s) have timeouts which either exceed this IO_timeout value or are not integer
		     multiples of this value.

   Shared Volume Group Considerations
       For volume group version 1.0 and 2.0, cannot be used if the volume group is activated in shared mode.  For volume groups  version  2.1  (or
       higher), can be performed when activated in either shared, exclusive, or standalone mode.

       Note that the daemon must be running on all the nodes sharing a volume group activated in shared mode.  See lvmpud(1M).

       LVM shared mode is currently only available in Serviceguard clusters.

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

       Change the permission of a logical volume to read-only:

       Change the allocation policy of a logical volume to nonstrict:

       Turn the mirror write cache off on a logical volume:

       Change the IO timeout value of a logical volume to 1 minute (60 seconds):

WARNINGS

       For root, swap or dump logical volumes, the allocation policy is always contiguous.  This attribute cannot be changed with

       By  setting mirror consistency recovery off, crash recovery time will be reduced.  After a system crash the mirrored logical volume will be
       available, but there may not be consistent data across each mirror copy.  The only types of data that can safely be put on a mirrored logi-
       cal volume with mirror consistency recovery turned off are:

       o  data not needed after a crash, such as swap or other raw scratch data, or

       o  data	that  an  application itself will automatically reconstruct; for example, a raw logical volume for which a database keeps a log of
	  incomplete transactions.

SEE ALSO

       lvcreate(1M), lvdisplay(1M), lvextend(1M), lvmpud(1M).

																      lvchange(1M)