To process documents received by a serial trigger in publishing order across a cluster or non-clustered group of Integration Servers , Universal Messaging delivers only one document at a time to an instance of the trigger. When an instance of serial trigger in the cluster or non-clustered group of Integration Servers receives a document, instances of that serial trigger that reside on other Integration Servers will not receive a document until the distributed document is processed and acknowledged. Because the serial trigger processes only one document at a time across the cluster or group, this routing approach ensures that documents from the same publisher are processed in the same order in which the documents were published.

A serial webMethods messaging trigger in Integration Server corresponds to a serial durable subscription on Universal Messaging. In Universal Messaging Enterprise Manager, the durable subscription for the trigger has the Serial check box selected. With a serial durable subscription, multiple consumers (triggers) can connect to the durable subscription. However, Universal Messaging delivers one document at a time across all the consumers for the durable subscription. Universal Messaging does not necessarily distribute documents for a serial trigger in a strict round-robin fashion. Rather, Universal Messaging may distribute several documents in a row to one consumer, several more documents in a row to another consumer, and so forth. This approach provides processing in publication order by publisher and also allows documents to be distributed across the cluster or non-clustered group of Integration Servers in a load-balanced fashion over time.