The second subkey that you can create is Aging Clean Interval (of REG_DWORD
type). This subkey controls how often (in seconds) Exchange attempts to purge
expired indexes. By default, Exchange 2003 attempts to purge expired indexes
once every 24 hours.
Typically, you should leave both of these registry keys alone. There are times
when it may be prudent to decrease the Aging Keep Time value from the default
period of 40 days, though. If a folder contains too many cached searches, back
links, restrictions, and the like, client response times become very slow.
If client response times become extremely slow and you start receiving Messaging
API (MAPI) errors that contain the phrase Client Operation Failed, decreasing
the Aging Keep Time period might fix the problem. Another symptom that might
indicate that you should decrease the Aging Keep Time period is if response
time is slow when accessing some of the folders within a store but normal for
other folders in the same store.
You can decrease the Aging Clean Interval so that Exchange will purge expired
indexes more frequently, but I don't recommend doing so unless advised by Microsoft
Product Support Services (PSS) because purging expired indexes can be resource
intensive.
Resolving Message Conflicts Within Public Folders
One of the more obscure Exchange maintenance tasks is resolving message conflicts
in public folders. The idea is that public folders can be replicated across
multiple servers. If two or more replicas of a message within a public folder
are simultaneously modified, the message is said to be in conflict.
Exchange gives the public folder owner a specific amount of time to resolve
the conflict manually. This period of time is called the conflict age limit.
If the public folder owner doesn't resolve the conflict within that period of
time, the resolve message conflicts maintenance task will resolve the
conflict automatically according to an internal set of rules.
You can set or modify the conflict age limit by making a change to the registry.
To do so, go to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\servername\Public-GUID registry subkey and create a REG_DWORD value named Replication Folder
Conflict Age Limit. Assign it a value that reflects the number of days that
messages are allowed to remain in conflict.
Removing Expired Messages from Public Folders
The final maintenance task that I want to talk about is that of removing expired
messages from public folders. The message-expiration period is set on a per-folder
basis, so there's no registry subkey that lets you globally adjust the expiration
period. However, you can create a registry value that controls how often Exchange
flushes expired messages from public folders. Again, be careful using this setting
because it can disrupt other maintenance tasks.
To set the message-removal frequency, go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\servername\Public-GUID
and create a REG_DWORD value named Replication Expiry. Assign it a value that
reflects the number of milliseconds between message-removal periods.
Automated Doesn't Mean Hands Off
As you can see, scheduled maintenance is vital to the integrity and performance
of Exchange's IS. By understanding how the automated maintenance process works
and using the techniques in this article, you can have more control over how
the server performs these tasks to optimize the process for your environment.