XADM: How the Location of Public Folders Affects Clients

• Microsoft Exchange Server, versions 5.0, 5.5

SUMMARY

This article discusses the process by which Exchange clients access public folders when the location of these folders changes. The location can change if an Exchange Server computer that is down for maintenance contains public folders that are replicated to other Exchange Server computers. The location also can change if a public folder is moved to another server by replicating it and then deleting it from the original server.

MORE INFORMATION

Two latencies are involved when the location of a public folder changes:

1. Directory replication latency to replicate this change to the other public folder servers in the location. If the servers are in the same site, this is typically 15 minutes at most.



2. Information store latency on the public folder servers to update their local cache of location information (called a sorted replica list) from their respective directories. This is done once every hour by default.
   
   On average, it takes about 40 minutes before the other servers are updated with the location change. After this happens, any client trying to open a public folder is given the sorted replica list (the list of locations where a public folder is available) according to the new location information.
   
   When a client logs on to Exchange and opens a public folder, it gets the fully sorted replica list for that public folder from its public folder hierarchy server and tries to connect to the replicas in approximately the order of the list. The client does not save a cache of replica servers for public folders. It gets this information from its hierarchy server each time a folder is opened.
   
   The client does have a cache of servers that it "knows" are down (when it fails to connect). The client tries to avoid these servers as much as possible while trying to connect to servers for content. Approximately every hour, the client attempts to poll these downed servers to see if they are back up.
   
   This means that if the server in your location is down, the client avoids it and goes to another location automatically without your having to change the location (after trying just once to open a folder on that downed server).
   
   The client switches back to the local server (the one in your location) if it becomes available while the client is running. This may affect what is seen in the client. The replicas of the public folder the client is using may not be identical, due to replication latency. So, if the client has a document open in the public folder and closes it before it switches to the local server, the changes may not be there when it is re- opened, or the document may not appear in the folder at all, depending on the situation. This is due to replication latency.

Additional query words: pf

Keywords : XADM
Version : WINDOWS:5.0,5.5
Platform : winnt
Issue type : kbinfo