Finding the Compromise – the Adapter Framework - Applied SOA Patterns on the Oracle Platform - page 401

Mind you, we did not say "eliminated", as some ABCS elements remain dedic-
ated to really weird things. Actually, that's what the Adapter framework is for.
• And one more thing—RRD's Event Handling System ( EHS ) solution is com-
pletely portable. It can be implemented on any Oracle DB (including XE). Al-
though it was not our first (or even second) goal, this option is quite positive from
a budget planning perspective.
With decoupled message construction queue and the native BES queue handler, the mes-
sage construction sequence will be as presented as follows:
A vendor-neutral architectural perspective must be extended with aspects that are specific
to Oracle-based implementation, and specifically, with benefits emerged from tools stand-
ardization:
• One of the cornerstones of this approach of eliminating ABCS layer is Event
Detection. Although TIBCO is quite prominent for its Event-driven Architecture,
Oracle also has a good history of Event recognition solutions, naturally based on
DB products. Starting from 9 i , Oracle provide CDC in an almost identical way as
described previously, based on triggers, change tables, and mostly suitable for the
ETL pattern. Remember, ETL is what we are trying to avoid here. From 10g , the
approach was enhanced by asynchronous feeds from changes detected into the
redo logs. The advantage is obvious—the CDC is not part of the transaction any-
more. Together with Oracle Streams, the CDC is capable to detect and propagate
the changes to subscribers. In general, tables change history trace functionality
was possible because of the new DBMS_FLASHBACK package. In 11g , synchron-
ous change data capture was introduced. Still, to understand the meaning of the