A common application requirement is to present messages to a channel for processing in an order that is not directly related to the order of their arrival at the prior channel. For example:
Underlying these types of requirements is a system that receives in some intermixed sequence, is charged with not losing any messages, and desires to process the incoming messages in parallel. Parallelism loses the input ordering. However, single threading has an adverse impact on performance.
The Ordered listener is an iWay Service Manager (iSM) channel that alleviates these concerns of parallelism, retaining the required order, and collecting messages for a specific purpose for dispatch to the next channel. Messages can be dispatched as they become available, while retaining the order, or as an ordered group when the final message of the group is recognized. With the exception of the ordering facility, an ordered queue is similar to the commonly used internal queue, and it retains the characteristics of that type of channel. This includes support for low and high watermark tracking, passivation, inhibition, and so on.
It is the responsibility of the application designer to determine the type of queue required and to place messages on the queue appropriately for the application.