Abstract The WLS JMS Unit-of-Order feature (UOO) is well documented in various papers and blogs; it mainly enables numerous message producer to group messages into a single unit that is processed sequentially in the order the messages were created. Until message processing for a message is complete, the remaining unprocessed messages for that Unit-of-Order are blocked. This behavior makes the usage of UOO essential in cases that a specific processing order must be adhered…