Exception destination

An exception destination is the location where messages that are not delivered to their original intended destination are sent for safekeeping. Exception destinations prevent the loss of messages that fail to get sent to their intended destinations.

If a message cannot be delivered to its intended bus destination, it can optionally be rerouted to an exception destination. You have three options when configuring exception destinations:
  1. Use the default exception destination belongs to each messaging engine.
  2. Specify a non-default exception destination.
  3. Set it to none, that is, disable it.
Each messaging engine has a default exception destination called _SYSTEM.Exception.Destination.me_name. When you create a messaging engine a default exception destination for that messaging engine is automatically created. It stores messages that cannot be delivered for bus destinations that are localized to the messaging engine. This default exception destination allows the administrator to access all messages that cannot be delivered for a messaging engine, in a single location.
Note: It is not possible to modify the default exception destination and you should not delete it.

You can also configure each bus destination so that it has a non-default exception destination. This enables administrators to access at a unique place messages that cannot be delivered for the bus destination. An exception destination must be a queue destination, but can be either local or remote. The exception destination must already exist before you configure another bus destination to use that exception destination. If the exception destination is not a queue, or if it has been deleted when the message arrives, undeliverable messages are rerouted to the default exception destination for the messaging engine.

In the third case where the exception destination has been disabled, there is no alternative destination to route if the messages cannot be delivered. The messaging engine repeatedly attempts to deliver to the target destination.
Note:
  • Best-effort messages are always discarded if they cannot be delivered to their target destination, that is, they will never make use of an exception destination.
  • A message cannot be available to consumers until it is successfully delivered to a destination.

The service integration bus cannot guarantee the ordering of messages sent to an exception destination. Because of this, if message order is important, you can configure a bus destination so that it does not use an exception destination. In this case, the Maximum failed deliveries limit specified for the destination is ignored, and the message remains available to consumers. Synchronous consumers repeatedly attempt to get the message; message-driven beans and other asynchronous consumers repeatedly attempt consume the message. This can cause an increased load on the system. This situation continues until either the message is removed from the destination (for example, by an administrator using the WebSphere® Application Server administrative console) or if the consumer is subsequently able to process the message without rolling back.

Published messages are discarded if there are no subscribers.

For related information, see Specifying an exception bus destination.




Related concepts
Learning about bus destinations
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Last updated: Aug 29, 2010 10:43:27 PM CDT
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