Information Technology Reference
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has its disadvantages as well. Because the server side does not block the
clients, they can continue to accept requests even if they cannot keep pace
with them, thus risking an overload situation.
MOM products are proprietary products and have been available from the
mid-1980s. Therefore, they are incompatible with each other. Using a single
product results in dependence on a specific vendor; this can have negative
influence on flexibility, maintainability, portability, and interoperability.
MOM product must specifically run on each and every platform being inte-
grated. Not all MOM products support all platforms, operating systems, and
protocols. However, Java platform provides ways to achieve relatively high
independence from a specific vendor through a common interface, used to
access all middleware products—the Java Message Service (JMS).
MOM is particularly suitable for integrating applications by reason of fea-
tures like the following:
Transparent cooperation of heterogeneous systems : The integration bro-
ker provides transformation software to transform application data
running under diverse programming environments, operating sys-
tems, and hardware platforms.
Prioritization of requests : All messages in an MOM environment may
have priority attached to them. This forces higher-priority messages
to be processed before lower-priority messages sent at an earlier
time.
Automatic message buffering and flow control : A distributed application
often will need to read messages from diverse applications and pro-
grams. To support this undertaking, each application can have mes-
sage queues that transparently buffer the messages when there are
variable traffic rates, providing automatic flow control.
Persistent messaging : This enables reliability and ensures that mes-
sages are guaranteed to be delivered at most once to their subscribers.
Flexibility and reliability : Flexibility with MOM is achieved because
an application can send its messages whenever it decides, inde-
pendently of the recipient's availability. Senders and recipients are
independent and thus unattached. Reliability is achieved because a
persistent message is never lost.
Load balancing : The asynchronous nature of MOM enables flexibil-
ity for load balancing. Load balancing is achieved as messages can
be forwarded from a relatively busy application system to a less
busy one. Dynamic load balancing can be designed into an MOM
environment using selected algorithms including least busy and
round-robin . This results in a cost-effective use of network facili-
ties. In addition, the load balancing facility generates highly avail-
able message queues and enables an effective peak-hours network
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