# Fast Mirror Mode

When you use the DAH only for requesting information from child servers, you can run it in fast mirror mode to improve performance.

In fast mirror mode, DAH does not perform any extra processing on actions. It simply distributes actions between child servers, either with load balancing or failover. In this case, you can use DAH only for requesting information from child servers.

When running the DAH in fast mirror mode:

- You must not send state-changing actions to the DAH. For example, you must not use the action parameters `Delete`, `State`, `StoreState` and so on.

- You must not use actions that require DAH to perform extra processing on actions. For example, you must not use the action parameters `Template`, `EncryptResponse`, `Output` and so on.

- You must not use action parameters that use document IDs (such as the `ID` parameter).

- You must not use distributed actions (actions sent to all child servers) or asynchronous actions.

To run the DAH in fast mirror mode

1. Open the DAH configuration file in a text editor.

2. In the `[Server]` section, set the `MirrorMode` parameter to `True`.

3. In the `[Server]` section, set the `FastMirrorMode` parameter to `True`.

4. In the `[Server]` section, set the `DistributionMethod` setting to determine how the DAH distributes the actions that it receives to the connected IDOL Servers.

   For details of the options available for the `DistributionMethod` parameter, see Run the Distributed Action Handler in Mirror Mode.

5. Save and close the configuration file.

6. Restart the DAH for your changes to take effect.

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