Q: Can I make a read-only domain controller a Global Catalog server?
A: Yes. Because a Global Catalog (GC) server is essentially a read-only copy of the partial attribute set of all domains in a forest, running it on a read-only domain controller (RODC) is fully supported. However, some applications won't work correctly with a GC server on an RODC. Therefore, it's important to check the supportability of your applications with a GC server running on an RODC.