It is a compound key of JMSPriority and arrival order.
JMS only guarantees ordering on initial receipt. If you nack
(negatively acknowledge) a message all bets are off.
but i would like to ask u one more question suppose the message i'm sending is set to the priority "5" and is in the AUTO_ACKNOWLEDGE mode ... then JMS gaurantees that message will recieve FIFO at the the subscriber side ....?