Microsoft Message Queuing duplicate message removal mechanisms (255546)

SUMMARY

When you run Microsoft Message Queue Server version 1.0 on Windows NT Server 4.0 with Service Pack 6 installed or MSMQ version 2.0 on Windows 2000, Microsoft Message Queuing monitors for duplicate messages and removes them.

The behavior described in this article only effects non-transactional messages. The delivery for transactional messages is not altered or affected by the caching mechanism described in this article.

MORE INFORMATION

The Microsoft Message Queuing Queue Manager caches messages sent to an Microsoft Message Queuing computer and removes any incoming messages that are duplicates of the messages in the cache. By default, this cache has a size of 10,000 messages and is purged every 30 minutes. Any messages older than the purge interval are removed from the cache during the purge operation. The cache is stored in memory and is reset if you restart the computer. Memory use by the caching mechanism is very efficient, as the cache consists of computer and message identifiers and does not store the entire message.

The purge interval and cache size values can be changed through the following registry settings:

HKEY_LOCAL_MACHINE\Software\Microsoft\MSMQ\Parameters\RemoveDuplicateSize: Specifies the cache size for removing duplicate messages. The default is 10,000 incoming messages.
HKEY_LOCAL_MACHINE\Software\Microsoft\MSMQ\Parameters\RemoveDuplicateCleanup: Specifies the cleanup interval for removing duplicate messages. The default time is 30 minutes.

Setting the RemoveDuplicateSize registry value to 0 disables the mechanism for removing duplicate messages.

Note: This information reflects the current implementation of this mechanism and may be subject to change in future versions of Microsoft Message Queuing.