Changing replication settings for the bunker Secondary


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Changing replication settings for the bunker Secondary

In normal operating conditions, the bunker acts in a Secondary role, and receives writes from the Primary. Like other Secondaries, the bunker Secondary has replication attributes, which determine the behavior of replication between the Primary and the Secondary. When you add a bunker to an RDS, it is configured as a Secondary and the replication attributes are set to the default values. For some of the attributes, the default values for a bunker Secondary are different than the default values for a standard Secondary.

To use values other than the defaults, change the replication settings between the Primary and the bunker Secondary using the vradmin set command. Each attribute setting could affect replication and must be set up with care. For detailed description of the replication attributes and how they affect replication, see Understanding replication settings for a Secondary.

The following table provides an overview of the replication attributes in the bunker scenario, including the default settings for a bunker Secondary.

Attribute	Meaning
`synchronous`	Sets the mode of replication for the bunker Secondary. When the synchronous attribute is set to `override`, replication is done synchronously. In this mode, the normal application write is not affected on the Primary when the link between the Primary and the bunker is down. We recommend setting the synchronous attribute to `override` to provide zero data loss under normal conditions. The default is `override`. When the synchronous attribute is set to `fail`, the application write fails when the link between the Primary and the bunker is down. This ensures that the bunker SRL is always as up-to-date as the Primary SRL and ensures zero RPO after bunker recovery on the Secondary if the Primary site crashes. To set up the bunker to replicate asynchronously, set the `synchronous` attribute to `off`. In this mode, use latency protection to limit how much the bunker can be behind the Primary.
`srlprot`	Sets SRL protection. `off` disables SRL protection. If the Primary SRL overflows for the bunker Secondary, the Secondary is detached, and the bunker cannot be used to track additional writes from the Primary. The default is `off`. `override` enables SRL protection. If the Primary and Secondary are connected, new writes are stalled until space becomes available in the SRL. If the Primary and Secondary are disconnected, VVR disables SRL protection and lets the SRL overflow. Because a bunker does not contain data volumes, a bunker cannot use a DCM to track changes in case of SRL overflow. Therefore, you cannot set the SRL protection to `dcm` or `autodcm` for a bunker.
`protocol`	Indicates the network connectivity between the bunker and Primary. If the bunker is replicating over IP, the protocol can be set to `UDP` or `TCP`. The default is `UDP`. If the storage is directly accessible by the Primary, for example, DAS or NAS, set the protocol to `STORAGE`.
`latencyprot`	Sets the latency protection for the bunker. Set the desired RPO value to make sure that the bunker never gets behind by more than this RPO. `off`, `fail`, or `override`. The default is `off`.
`latency_high_mark` `latency_low_mark`	Set when using latency protection. See the description of these attributes in The latencyprot attribute.
`packet_size`	Indicates the packet size used by VVR. The packet setting is only specified if the protocol is UDP. The default is 8400.
`bandwidth_limit`	Controls the amount of bandwidth used by VVR for replication to the bunker. The default bandwidth limit is none, indicating that VVR can use any available bandwidth.


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