Syncronous/Asyncronous Mode

As described in Request Queue Management, a client that sends multiple requests before waiting for the response from a previous request is not guaranteed to receive the responses in the order they were sent.

If a client wishes to send a request before waiting for the response to the previous one (asyncronous mode), then the client must populate the id attribute in the request with a transaction ID value that will be passed back in the response. The id attribute needs to be unique enough to the client to correlate a response to a request that was sent. The XML Data server will return the id passed in the response.

If a client wishes to send a single request and wait for the response before sending another one (syncronous mode), then the client does not need to populate the id attribute in the request, because the response will always be for the request last sent. The id attribute can be populated if desired, and it will be passed back in the response just as in asyncronous mode.