Why did I read message from queue whereas the sequence is not correct?

I encountered an issue where sometimes the lookupid will jump when I read message from queue by lookupID.

The process is that I will use MQ_LOOKUP_PEEK_FIRST as the action parameter to read first message, and then use MQ_LOO开发者_StackOverflow中文版KUP_PEEK_NEXT to read subsequent message until the queue is empty, then I will start using MQ_LOOKUP_PEEK_FIRST to read the first message.

The problem is sometimes I may read a message with lookupid which is bigger than the lookupid in the next message. How could it happen?

Just read the link below, looks like it proves what I think that MQ message could be out of order. http://www.ms-news.net/f2437/how-can-messages-appear-out-order-non-transacational-messages-11964070.html