DSAccess builds a list of domain controllers (DCs) and Global Catalogs (GCs) for Exchange 2000 Server to use for retrieving information from Active Directory (AD). To build the list, DSAccess follows these steps:
- Call the Directory Service (DS) Locator Service.
- Retrieve the list of all DCs and GCs from the local AD site.
- Contact each server in the list.
- Cache up to 10 active DCs and 10 active GCs.
- Reorder the active GC list so that domain-local GCs are at the top of the list.
- Use the cached DC and GC server list on a simple round-robin basis.
Here are some important enhancements and exceptions to this process:
- If DSAccess can't locate a GC in the local AD site, it uses GC servers from the local domain.
- If DSAccess can't locate a GC in the local AD site or the local domain, it uses GC servers from anywhere in the forest.
- If responses from cached servers take more than 5 seconds, DSAccess marks the server as SLOW and sends all requests synchronously.
- If the cached server is unavailable, DSAccess marks the server as DOWN and retries it at a specified interval (e.g, 5 minutes, 10 minutes, 25 minutes).
- DSAccess adds new GC servers to the cache as they become available on the network.
- GCs are marked as UP if they're available, FAST if they respond to directory queries within 5 seconds (within 2 seconds for Exchange 2000 Server Service Pack 1—SP1), and InSync if all intraforest replication has taken place.