What causes this discrepancy?

View the Exhibit.

A user has configured Mediator M1 to receive and route product Information from System X into its
internal applications in chronological order. For each product1 M1 receives one create number of
“update” events from an AQ Queue via a JMS adapter. M1 can receive updates to the product at
any time of day.

The user claims that incoming messages for each product are received and processed in the
correct chronological order 95% of the time. However, the messages are being processed out of
order 5% of the time. This results in critical errors in the target systems. The user expects all
messages pertaining to a product to be unconditionally processed In the order of arrival at M1.
What causes this discrepancy?

A.
The user is running on a four node SOA cluster and has not configured the inbound JMS
adapter to be a singleton.

B.
The user is running a single-node SOA environment but has configured the number of inbound
adapter threads to be a value greater than 1.

C.
The given Mediator configuration does not address this sequencing requirement.

D.
The user has configured resequencer worker threads to a value greater than 1 for the Mediator
service engine.

Explanation:
* From the exhibit we see:
Resequence Level: component
Resequence Mode: Best Effort
* It is important to note that the messages to outbound services of the Oracle Mediator service
component configured for best effort resequencing are not guaranteed to arrive in order of a
sequence ID. At any given time, a snapshot of the available messages is taken and sequencing is
performed only on those messages. Therefore, unlike a standard resequencer, it is not guaranteed
that a message with a lesser sequence ID value is sent before a message that ha a greater
sequence ID value but that arrived earlier. Messages with a lesser sequence ID value that arrive
later might be processed in the following cycle when a snapshot of available messages is taken
again and the messages are reordered.