Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Chapter 8, Administering Volumes
Upgrading Existing Volumes to Use Version 20 DCOs
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3. Repeat the following steps to upgrade each volume within the disk group as required:
a. If the volume to be upgraded has a traditional DRL plex or subdisk (that is, the
DRL logs are not held in a version 20 DCO volume), use the following command
to remove this:
# vxassist [-g diskgroup] remove log volume [nlog=n]
Use the optional attribute nlog=n to specify the number, n, of logs to be removed.
By default, the vxassist command removes one log.
b. For a volume that has one or more associated snapshot volumes, use the
following command to reattach and resynchronize each snapshot:
# vxassist [-g diskgroup] snapback snapvol
If FastResync was enabled on the volume before the snapshot was taken, the data
in the snapshot plexes is quickly resynchronized from the original volume. If
FastResync was not enabled, a full resynchronization is performed.
c. Use the following command to turn off FastResync for the volume:
# vxvol [-g diskgroup] set fastresync=off volume
d. Use the following command to dissociate a version 0 DCO object, DCO volume
and snap objects from the volume:
# vxassist [-g diskgroup] remove log volume logtype=dco
e. Use the following command on the volume to upgrade it:
# vxsnap [-g diskgroup] prepare volume [ndcomirs=number] \
[regionsize=size] [drl=on|sequential|off] \
[storage_attribute ...]
The ndcomirs attribute specifies the number of DCO plexes that are created in
the DCO volume. It is recommended that you configure as many DCO plexes as
there are data and snapshot plexes in the volume. The DCO plexes are used to set
up a DCO volume for any snapshot volume that you subsequently create from the
snapshot plexes. For example, specify ndcomirs=5 for a volume with 3 data
plexes and 2 snapshot plexes.
The value of the regionsize attribute specifies the size of the tracked regions in
the volume. A write to a region is tracked by setting a bit in the change map. The
default value is 64k (64KB). A smaller value requires more disk space for the
change maps, but the finer granularity provides faster resynchronization.
To enable DRL logging on the volume, specify drl=on (this is the default setting).
If sequential DRL is required, specify drl=sequential.If DRL is not required,
specify drl=off.