HKEY_DYN_DATA

One version of Registry Editor, Regedit.exe, displays a sixth subtree, HKEY_DYN_DATA. This is a subtree of the Windows 95 and Windows 98 registries, but it is not used by Windows 2000. For more information about Registry Editor, see Using Regedt32.exe and Regedit.exe.

Placeholder for performance data lookups. This key has no corresponding physical hive.

Windows & .NET Magazine

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HKEY_DYN_DATA
HKDD is a fake key--it doesn't really exist. It serves as a convenient doorway to device driver, Win32 application, and native NT performance counters via the Registry API. When a Win32 program queries a value or key in HKDD, the request gets routed as an I/O request to the appropriate driver or Win32 program, which returns information that looks like the result of an authentic Registry access. The Performance Monitor (Perfmon) program accesses this root key to provide the intricate performance information it displays.