In general it is not necessary to create more than one WS-Notification
service in each service integration bus, however there are some cases where
it is useful to do so.
If you have multiple service integration buses defined in a cell and you
want to provide WS-Notification access to messaging resources defined on each
of the buses, then you must define a WS-Notification service on each of
the buses. This configuration of one WS-Notification service on each service
integration bus that needs WS-Notification access is the recommended approach.
It ensures that applications connected to different WS-Notification services
cannot pass information to each other, or cause interference.
You might choose to define multiple WS-Notification services on a single
bus in order to segregate groups of client applications into disjoint sets,
for example to meet one of the requirements listed below. However you should
use this pattern with care, because there are significant implications to
making this choice - in particular associated with the WS-Notification topic
namespaces that are defined on the WS-Notification service. For more information
about topic namespace patterns see Options for associating a permanent topic namespace with a bus topic space.
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Segregation of applications by using different namespaces. You can
use distinct topic namespace URIs (and equally, different service integration
bus topic spaces) in the two WS-Notification services to segregate the applications
that use each service. For more information, see 1 to 1 association between a service integration bus topic space and a topic namespace URI.
Note that segregation in this way can also be achieved by using a single WS-Notification
service.
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Enforced segregation of applications by using the same namespace.
The key advantage of defining multiple WS-Notification services on a single
bus comes from the ability to partition a collection of applications that
are written to use the same topic namespace into two (or more) distinct groups
that do not interact at all. This allows the applications connected to the
first WS-Notification service to operate completely isolated from those connected
to the second WS-Notification service, even though they are using the same
topic namespace, and quite probably the same set of topics. For more information, see
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Alternative JAX-RPC handler lists and outbound security settings.
These properties are specified for each WS-Notification service, rather than
for each outbound port. If you need alternative options for these properties
then you should create a separate WS-Notification service on the same bus
for each alternative outbound configuration.