Distribution in Mirror Mode

The diagram below represents a DAH run in mirror mode. In this setup, the DAH distributes actions to several identical IDOL Servers.

DAH system architecture (mirror mode)

The DAH distributes the actions according to the value of the DistributionMethod parameter in the DAH configuration file. You can use the following methods:

The DAH periodically checks IDOL servers that are down. If an IDOL Server has come online again (for example, because the hardware has been rebooted or the network connection repaired), the DAH adds it back into the list of active IDOL Servers.


The DAH always sends state-changing actions (actions that cause changes in a child server) to all child servers, to ensure that they remain consistent. The DAH queues state-changing actions for any child servers that are not running, and sends these actions before it distributes new actions to the child server.

The DAH cannot always queue CategoryMove and CategorySetDetails actions. It returns an error if child servers stop running.