[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue.
The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime.
For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707
Topic Last Modified: 2010-05-25
The Microsoft Exchange Best Practices Analyzer queries the Active Directory directory service to determine the value of the msds-isRODC attribute of all domain controllers on each site.
At least one writable domain controller is required for each site. If the msds-isRODC attribute is not set to FALSE on any domain controllers on a site, every domain controller on that site is a read-only domain controller (RODC). In this case, the Analyzer tool generates a warning message.
To resolve this issue, you must add one writable domain controller to the site. You cannot change an RODC to a writable domain controller.