A traditional DRL log is configured within a DRL plex. A version 20 DCO volume cannot be used in conjunction with a DRL plex. The version 20 DCO volume layout includes space for a DRL log.

To put dirty region logging (DRL) into effect for a mirrored volume, you must add a log subdisk to that volume. Only one log subdisk can exist per plex.

To add DRL logs to an existing volume, use the following command:

# vxassist [-b] [-g diskgroup] addlog volume logtype=drl \
   [nlog=n] [loglen=size]

If specified, the -b option makes adding the new logs a background task.

The nlog attribute specifies the number of log plexes to add. By default, one log plex is added. The loglen attribute specifies the size of the log, where each bit represents one region in the volume. For example, a 10 GB volume with a 64 KB region size needs a 20K log.

For example, to add a single log plex for the volume vol03 in the disk group mydg, use the following command:

# vxassist -g mydg addlog vol03 logtype=drl

When you use the vxassist command to add a log subdisk to a volume, a log plex is created by default to contain the log subdisk. If you do not want a log plex, include the keyword nolog in the layout specification.

For a volume that will be written to sequentially, such as a database log volume, use the following logtype=drlseq attribute to specify that sequential DRL will be used:

# vxassist -g mydg addlog volume logtype=drlseq [nlog=n]

After you create the plex containing a log subdisk, you can treat it as a regular plex. You can add subdisks to the log plex. If you need to, you can remove the log plex and log subdisk.