You want to know the schema master in active directory
You can use the Active Directory Schema Snap-in. You will find the name of the Schema Master server between  brackets in the main node.
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About the Author
Author: Wim Peeters - Keskon GmbH & Co. KG
Wim Peeters is electronics engineer with an additional master in IT and over 30 years of experience, including time spent in support, development, consulting, training and database administration. Wim has worked with SQL Server since version 6.5. He has developed in C/C++, Java and C# on Windows and Linux. He writes knowledge base articles to solve IT problems and publishes them on the Lubby Knowledge Platform.