Advanced Queuing - Oracle

Modeling Queue Entities
Figure 7–6 Dequeuing of Specified Messages by Specified Recipients
Queue Table
Subscriber list: s1, s2, s3
Recipient list: r1, r2
Queue Subscribers
Msg 1
Msg 2
Msg 3
Msg 4
Msg 5
Msg 6
Msg 7
We earlier referred to subscribers as implicit recipients in that they are able to
dequeue all the messages placed into a specific queue. This is like subscribing to a
magazine and thereby implicitly gaining access to all its articles. The category of
consumers that we have referred to as recipients may also be viewed as explicit
recipients in that they are designated targets of particular messages.
Figure 7–7 shows how Oracle AQ can adjust dynamically to accommodate both
kinds of consumers. In this scenario Application B and Application C are implicit
recipients (subscribers). But messages can also be explicitly directed toward specific
consumers (recipients) who may or may not be subscribers to the queue. The list of
such recipients is specified in the enqueue call for that message and overrides the
7-10 Oracle9i Application Developer’s Guide - Advanced Queuing
R1
R2
S1
S2
S3