Active Directory For Dummies, 2nd Edition
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Active Directory uses a multiple-master model, and usually, domain controllers (DCs) are equal with each other in reading and writing directory information. However, certain roles cannot be distributed across all the DCs, meaning that changes can't take place on more than one domain controller at a time. Some domain controllers, therefore, do assume a single-master operations role — known as operations masters in Active Directory.

The five categories of operations master roles are:

  • Schema master (one per forest): Maintains the master copy of the schema.

  • PDC emulator (one per domain): Emulates a primary domain controller for backward compatibility with Windows NT.

  • Domain naming master (one per forest): Tracks object names throughout a forest to ensure that they're unique. Also tracks cross-references to objects in other directories.

  • Infrastructure master (one per domain): Tracks object references among domains and maintains a list of deleted child objects.

  • Relative identifier (RID) master (one per domain): Tracks the assignment of SIDs (security identifiers) throughout the domain.

Usually, the first domain controller that you create in the first domain assumes the operations master roles. You can assign these roles to other domain controllers in the domain or forest, but only one domain controller at a time can hold each operation's master role.

About This Article

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About the book authors:

Steve Clines, MCSE, MCT, has worked as an IT architect and engineer at EDS for over 18 years. He has worked on deployments of more than 100,000 seats for both Active Directory and Microsoft Exchange Server. Steve is the author of MCSE Designing a Windows 2000 Directory Services Infrastructure For Dummies, which is a study guide for the 70-219 MCP exam. He also maintains the Confessions of an IT Geek blog at http://itgeek.steveco.net.

Marcia Loughry, MCSE and MCP+I, is a Senior Infrastructure Specialist with a large IT firm in Dallas, Texas. She is president of the Plano, Texas BackOffice User Group (PBUG) and a member of Women in Technology International. Marcia received her MCSE in NT 3.51 in 1997 and completed requirements for the NT 4.0 track in 1998.
Marcia has extensive experience working with Windows NT 3.51 and 4.0 in enterprises of all sizes. She is assigned to some of her firm’s largest customers in designing NT solutions and integrating UNIX and NetWare environments with NT.

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