# Determine the State of Child Servers

The DIH regularly pings all its child IDOL servers to determine their state; running (up) or not running (down). In mirror mode, if a server is down, the DIH queues the data for that server, and indexes the data into the server when it is available again. In non-mirror mode, the DIH redistributes the data among the available servers. In this case, it also queues any updates to documents that have already been indexed, and sends the updates when the server is available again.

You can configure how often the DIH checks the state of its child servers. Set the `PingInterval` parameter in the `[Server]` section of the DIH configuration file to the time interval between checks. The default value is 20 seconds.

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