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.
Table: Mode of replication and the state of the RLINK summarizes how the state of the RLINK affects the mode of replication.
Table: Mode of replication and the state of the RLINK
Value of synchronous Attribute |
When RLINK is Connected |
When RLINK is Disconnected |
---|---|---|
override |
Synchronous |
Asynchronous |
off |
Asynchronous |
Asynchronous |
fail |
Synchronous |
I/O error to application |
synchronous=off
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.
synchronous=override
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 would prefer to set the synchronous attribute to override rather than setting it to fail.
Warning: |
If you use the synchronous=fail mode, you must read the section about synchronous mode considerations. |
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.