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To prepare an application volume for dirty region logging (DRL) and instant snapshot operations, a data change object (DCO) and DCO volume must be associated with the volume.
The procedure in this section describes how to add a version 20 DCO and DCO volume to an application volume that you previously created in a disk group with a version number of 110 or greater. If you are creating a new volume in a disk group with a version number of 110 or greater, you can specify the co-creation of a DCO and DCO volume and enabling of DRL.
See Creating a volume for use with snapshots and DRL.
You may need an additional license to use the DRL and FastResync features.
Use the following command to add a version 20 DCO and DCO volume to an existing volume:
# vxassist [-g diskgroup] [-P storage_pool] addlog volume \
[nlog=number] logtype=dco [regionsize=size] \
The nlog 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 plexes in the volume. For example, specify nlog=3 for a volume with 3 data 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=yes. If sequential DRL is required, specify drl=sequential.
You can also specify vxassist-style storage attributes to define the disks that can and/or cannot be used for the plexes of the DCO volume.