Replication Long Backfill Request Timeout Retry value changed
[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 https://go.microsoft.com/fwlink/?linkid=34707.]
Topic Last Modified: 2005-11-18
The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine if the Replication Long Backfill Request Timeout Retry key has been modified from the default value:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\<servername>\Public-<GUID of Public Store>\Replication Long Backfill Request Timeout Retry**
If the Exchange Server Analyzer finds Replication Long Backfill Request Timeout Retry to be present, a non-default configuration message is displayed.
By default, Replication Long Backfill Request Timeout Retry does not exist. Backfilling occurs when a public folder store determines that it has not received all of the updates for a replicated folder (or for the hierarchy) and must retrieve the missing updates from another store.
To streamline the backfill process, Exchange Server stores information about missing updates in the backfill array. The backfill array stores this information for a specified length of time (called the backfill time-out). If the missing updates arrive in subsequent replication messages during this time, they are removed from the backfill array. The table lists the default backfill time-out values, which depend on where the missing updates exist and whether they have been requested before.
| Type of request | Content exists on a store in the local site | Content exists on a store in a remote site |
|---|---|---|
Initial backfill |
6 hours |
12 hours |
First backfill retry |
12 hours |
24 hours |
Subsequent backfill retries |
24 hours |
48 hours |
If the backfill time-out expires and the updates are still missing, Exchange Server 2003 creates one or more backfill requests and determines which servers to use as backfill sources.
To select a server (or servers) to use as a backfill source, Exchange Server 2003 first creates a list of all of the servers that have replicas of the folder, and then sorts the list according to the following sequence of criteria:
Sort according to server status Servers that are down or unavailable drop to the end of the list.
Sort according to preferred backfill server If any; this feature is only available in Exchange Server 2003 and later. Exchange Server 2003 checks the public folder store object in the Active Directory® directory service for a preferred backfill server. This setting is seldom used. In most circumstances, the backfill process operates most efficiently if Exchange Server 2003 selects a backfill server automatically. Most deployments of Exchange Server 2003 do not need a preferred backfill server. Microsoft Product Support Services can provide a script that sets a preferred backfill server if your deployment requires it.
Sort according to transport cost (lowest to highest) Servers in the same site have priority over servers in remote sites. The transport cost of a server is calculated by the Exchange Server 2003 routing engine, and is normally used to calculate the most efficient way to deliver a message. Note that in versions of Exchange prior to Exchange Server 2003, transport cost has lower priority and is only considered after Exchange version and number of available changes.
Sort according to Exchange version (newest to oldest)
Sort according to the number of necessary changes that are available on the server (largest to smallest) Servers that do not have any of the missing changes are dropped from the list.
If one server does not have all of the required changes, Exchange Server 2003 selects the next server in the sorted list and sends a backfill request to that server as well. This process is repeated until all of the changes have been requested. This feature is only available in Exchange Server 2003 and later; previous versions of Exchange send backfill requests to one server at a time if no single server holds all of the missing updates for a specific folder. After each request, previous versions of Exchange wait for the retry time-out (from 24 through 48 hours) to elapse before sending the next request.
If the selected server does not respond to the backfill request, the store marks that server as down and repeats the selection process. Servers marked down drop to the end of the list.
The Replication Long Backfill Request Timeout Retry value represents the time-out value the public folder store uses when sending a backfill request for data that is not available in the same Exchange site, and when this request is a retry of a previous backfill request. The value, in seconds, must be between 900 and 2592000 seconds (30 days); the default value is 172800 seconds (48 hours).
Important
This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.
To reset the Replication Long Backfill Request Timeout Retry registry key
Open a registry editor, such as Regedit.exe or Regedt32.exe.
Navigate to: HKLM\System\CurrentControlSet\Services\MSExchangeIS\<servername>\Public-<GUID of Public Store>**
Examine or edit the value for Replication Long Backfill Request Timeout Retry.
The value for this registry entry is in seconds. To return to the default value, you should delete Replication Long Backfill Request Timeout Retry and restart the Microsoft Exchange Information Store service.
Before you edit the registry, and for information about how to edit the registry, see the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (https://go.microsoft.com/fwlink/?linkid=3052&kbid=256986).
For more information about public folder replication, see "Controlling Exchange Server 2003 Public Folder Replication" in Working with the Exchange Server 2003 Store (https://go.microsoft.com/fwlink/?LinkId=47595).