Advanced Queuing - Oracle

JMS Message Producer Features
JMS Message Producer Features
Priority and Ordering of Messages
Time Specification - Delay
Time Specification - Expiration
Message Grouping
Priority and Ordering of Messages
The message ordering dictates the order in which messages will be received from a
queue or topic. The ordering method is specified when the queue table for the
queue or topic is created (see "Creating a Queue Table" in Chapter 9,
"Administrative Interface"). Currently, AQ supports ordering on two of the message
attributes:
Priority
Enqueue time
When combined, they lead to four possible ways of ordering:
FIFO Ordering of Messages If enqueue time was chosen as the ordering criteria,
then messages are received in the order of the enqueue time. The enqueue time is
assigned to the message by AQ at message publish/send time. This is also the
default ordering.
Priority Ordering of Messages If priority ordering is chosen, each message will be
assigned a priority. Priority can be specified as a message property at publish/send
time by the Message Producer. The messages will be received in the order of the
priorities assigned.
First-In, First-Out (FIFO) Priority Ordering A FIFO-priority topic/queue can also
be created by specifying both the priority and the enqueue time as the sort order of
the messages. A FIFO-priority topic/queue behaves like a priority queue, except if
two messages are assigned the same priority, they will be received in the order of
their enqueue time.
Enqueue Time Followed by Priority Messages with the same enqueue time will
be received according to their priorities. If the ordering criteria of two message is
the same, then the order they are received is indeterminate. However, AQ does
ensure that messages send/published in the same session with the same ordering
criteria will be received in the order they were sent.
12-56 Oracle9i Application Developer’s Guide - Advanced Queuing