# Requirements

This section describes the software and hardware requirements for IDOL and the DAH.

## Supported Platforms

IDOL runs on a variety of Windows and UNIX platforms. For details of supported platforms, refer to the IDOL Server Release Notes.

NOTE: To run the DAH on Microsoft Windows operating systems, you must install the `msvcrt.dll` library.

## IDOL Servers Required

You must have at least two IDOL Servers installed for the DAH to distribute to.

NOTE: A single DAH can distribute to up to 1,024 IDOL Servers. However, Micro Focus recommends that you use the DAH to distribute to no more than 16 IDOL Servers, because distributing to a larger number can have a negative impact on processing time.

## State-Changing Actions File

In mirror mode, DAH uses the `sca.dat` file to determine the state-changing actions that it must distribute to all child servers.

When you are running the DAH in mirror mode, you must ensure that the `sca.dat` file is present. By default, this file must be in the same directory as the DAH, but you can also set the `SCAFileDirectory` configuration parameter to the location of this file.

If you upgrade DAH, you might need to download a new `sca.dat` file from the Micro Focus Big Data customer support site. Refer to the Distributed Action Handler Release Notes.

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