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This section explains how to use the Full Synchronization feature of VVR to synchronize the Secondary completely and start replication. Full synchronization compresses zeroes while processing the data and hence proves beneficial when a large part of the Primary data volumes contain zeroes. However, we recommend that you use Automatic Synchronization to synchronize the Secondary because its performance is better than Full Synchronization. Automatic Synchronization also handles network outages efficiently and continues even after the system reboots.
Full synchronization synchronizes the Secondary over the network when the Primary data volumes contain data and when the application is active or inactive. After the Primary and Secondary are synchronized, replication must be started.
By default, the vradmin syncrvg command synchronizes Secondary data volumes using difference-based synchronization. To perform a full synchronization, specify the -full option.
We recommend that you always use the -c option with the vradmin syncrvg command to synchronize the Secondary using full synchronization. The -c checkpoint option starts a checkpoint, synchronizes the data volumes, and ends the checkpoint after the synchronization completes. After the vradmin syncrvg command completes, use this checkpoint with the vradmin startrep command to start replication. To delete the Primary checkpoints, use the vxrvg checkdelete command.
The SRL must be large enough to hold the incoming updates to the Primary data volumes while the synchronization is in progress. The SRL might fill up and the checkpoint might overflow if the number of writes to the Primary data volumes is high when the Secondary is being synchronized.
A checkpoint that has overflowed becomes invalid and cannot be used to start replication. If the checkpoint overflows while synchronization is in progress, the vradmin syncrvg command must be issued again.
The vradmin syncrvg command can be used to synchronize multiple Secondaries at the same time. The vradmin syncrvg command displays the progress of the synchronization.
The vradmin syncrvg command synchronizes the volumes in an RVG. If a volume set is associated to an RVG, synchronizing the RVG only affects the component volumes of the volume set that are associated with the RVG. If the volume set includes component volumes that are not associated to the RVG, those volumes are not synchronized.
To synchronize the Secondary RVG with the Primary RVG using full synchronization with checkpoint
# vradmin -g diskgroup -full -c checkpt_name syncrvg \
local_rvgname sec_hostname....
Note that you can use the -c option with the vradmin syncrvg command when performing full synchronization, to automatically start a checkpoint with the specified name. After the data volumes are synchronized, the checkpoint is ended. This checkpoint can then be used to start replication using the vradmin startrep command.
The argument local_rvgname is the name of the RVG on the local host and represents its RDS.
The argument sec_hostname... is a space-separated list of the names of the Secondary hosts as displayed in the output of the vradmin printrvg command.
The argument checkpt_name specifies the name of the Primary checkpoint of your choice.
After the RLINKs are attached, the Secondary remains inconsistent until it has received all of the accumulated updates up to the checkend. While the Secondary is inconsistent, the inconsistent flag is set on the Secondary RLINK. After all updates up to the checkend have been received and applied at the Secondary, the inconsistent flag is cleared.
To view the status of synchronization, see Displaying the status of a Secondary.
Example—Synchronizing the Secondary using full synchronization with checkpoint
This example explains how to synchronize the Secondary RVG hr_rvg on the Secondary host london with the Primary RVG on host seattle.
To synchronize the Secondary RVG hr_rvg on london with its Primary RVG on seattle using full synchronization
Note that you can use the -c option with the vradmin syncrvg command when performing full synchronization, to automatically start a checkpoint with the specified name. After the data volumes are synchronized, the checkpoint is ended. This checkpoint can then be used to start replication using the vradmin startrep command.
The name checkpt_presync is the Primary checkpoint that you will create.