Finally, yougrant appropriate access privileges to users of applications that access
the data at the multiple sites.
Moving Data Between Distributed Systems | 313
Advanced Queuing
In the 1980s, message-oriented middleware (MOM) gained popular usage. MOM uses
messages to transmit information between systems. It doesn??™t require the overhead of
a two-phase commit because the MOM itself guarantees the delivery of all messages.
Products such as IBM??™s MQSeries store control information (message destination,
expiration, priority, and recipients) and the message contents in a file-based queue.
Delivery is guaranteed in that the message will remain in the queue until the destination
is available and the message is forwarded.
Oracle??™s Advanced Queuing (AQ) facility, first introduced with Oracle8 Enterprise
Edition and now part of Oracle Streams, provides a complete queuing environment
by storing the queue in the Oracle relational database. Advanced queues are Oracle
database tables that support queuing operations??”in particular, enqueue to create
messages and dequeue to consume them.
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