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You can set up VVR to replicate to a Secondary in synchronous or asynchronous mode by setting the synchronous attribute of the RLINK to override, off, or fail. The following table summarizes how the state of the RLINK affects the mode of replication:
By default, VVR sets the synchronous attribute to off. Setting the attribute of an RLINK to synchronous=off sets the replication between the Primary and the Secondary to asynchronous mode.
Setting the synchronous attribute to override puts the RLINK in synchronous mode and specifies override behavior if the RLINK is disconnected. During normal operation, VVR replicates in synchronous mode. If the RLINK is disconnected, VVR switches temporarily to asynchronous mode and continues to receive writes from the application and logs them in the SRL. After the connection is restored and the RLINK is up-to-date, the RLINK automatically switches back to synchronous mode. Most system administrators set the synchronous attribute to override.
Caution
You must read the section "Synchronous Mode Considerations" in the Veritas Volume Replicator Planning and Tuning Guide if you use the synchronous=fail mode.
Setting the synchronous attribute to fail puts the RLINK in synchronous mode and specifies the behavior if the RLINK is disconnected. During normal operation, VVR replicates in synchronous mode. If the RLINK is disconnected, VVR fails incoming writes to the Primary.