Tricks and Tweaks for Maintaining Exchange Databases

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.