The Automatic Synchronization feature enables you to transfer the data on the Primary to the Secondary over the network. You can synchronize the Secondary using automatic synchronization either when the application is active or inactive.
The Automatic Synchronization procedure transfers data in the Primary data volumes to the Secondary by reading the Primary data volumes from start to finish and sending the data to the Secondary.
Note Automatic Synchronization does not maintain the order of writes; therefore, the Secondary is inconsistent until the process is complete.
The Secondary becomes consistent after the automatic synchronization completes. To use Automatic Synchronization successfully, the network must be sized appropriately. Note that the synchronization will complete only if the Primary receives writes at a lesser rate than they can be sent to the Secondary. If the Primary receives writes at a faster rate than they can be sent to the Secondary, the synchronization might never complete, especially if the writes are dispersed widely in the volume.
This feature enables you to synchronize multiple Secondary hosts at the same time. When performing automatic synchronization to multiple Secondary hosts, synchronization proceeds at the rate of the slowest network.
VVR pauses synchronization if the Secondary fails or the network disconnects. If the Primary fails while synchronization is in progress, the synchronization continues from the point at which it had stopped when the Primary recovers.
Prerequisite for using Automatic Synchronization
startrep command when used with the option
-a enables you to start replication and automatically synchronize the Secondary data volumes with the Primary data volumes in an RDS; it brings the Secondary data volumes up-to-date with the Primary data volumes. You can use this command to synchronize the Secondary when the data volumes contain data and when the application is active or inactive. Replication to another Secondary can be started only after this automatic synchronization completes.
startrep command can be issued from any host in the RDS. To check the status and progress of the automatic synchronization, use the
status command on the Primary RLINK. For more information, see Displaying the status of a Secondary.
To synchronize the Secondary and start replication using automatic synchronization, issue the following command:
vradmin -g diskgroup
startrep local_rvgname sec_hostname
local_rvgname is the name of the RVG on the local host and represents its RDS.
sec_hostname is the name of the Secondary host displayed in the output of the
printrvg command. If the RDS contains only one Secondary, the
sec_hostname is optional.
Example—Using the Automatic Synchronization Feature
In this example, the data volumes in the Primary RVG
hr_rvg on host
seattle contain valid data and the application is active. To start replication and synchronize the Secondary RVG
hr_rvg on host
london, issue the following command:
vradmin -g hrdg -a startrep hr_rvg london
Notes on using automatic synchronization