Advanced Queuing - Oracle

General Features of Advanced Queuing
Setting Up Propagation Enable propagation from each publisher application queue.
To allow subscribed messages to be delivered to remote queues, the Order Entry
application enables propagation by means of the following statement:
execute dbms_aqadm.schedule_propagation(queue_name => 'OE.OE_bookedorders_que');
Publishing Messages Booked orders are published by the Order Entry application
when it enqueues orders (into the OE_booked_order_que) that have been
validated and are ready for shipping. These messages are then routed to each of the
subscribing applications. Messages are delivered to local queues (if specified) at
each of the subscriber applications.
Receiving Messages Each of the shipping applications and the Customer Service
application will then receive these messages in their local queues. For example,
Eastern Region Shipping only receives booked orders that are for East Coast
addresses or any U.S. order that is marked RUSH. This application then dequeues
messages and processes its orders for shipping.
Support for Oracle Real Application Clusters
Real Application Clusters can be used to improve AQ performance by allowing
different queues to be managed by different instances. You do this by specifying
different instance affinities (preferences) for the queue tables that store the queues.
This allows queue operations (enqueue and dequeue) on different queues to occur
in parallel.
The AQ queue monitor process continuously monitors the instance affinities of the
queue tables. The queue monitor assigns ownership of a queue table to the specified
primary instance if it is available, failing which it assigns it to the specified
secondary instance.
If the owner instance of a queue table terminates, the queue monitor changes
ownership to a suitable instance such as the secondary instance.
AQ propagation is able to make use of Real Application Clusters, although it is
transparent to the user. The affinities for jobs submitted on behalf of the
propagation schedules are set to the same values as that of the affinities of the
respective queue tables. Thus a job_queue_process associated with the owner
instance of a queue table will be handling the propagation from queues stored in
that queue table, thereby minimizing pinging. Additional discussion on this topic
can be found under AQ propagation scheduling (see "Scheduling a Queue
Propagation" on page 9-71 in Chapter 9, "Administrative Interface").
8-30 Oracle9i Application Developer’s Guide - Advanced Queuing