There are many, many new features to be found in the most recent PeopleTools release from Oracle. One such improvement/addition to the development toolset within PeopleTools is the Application Engine Action Plug-in. This functionality allows you to change the SQL or PeopleCode actions of any Application Engine without directly customizing or changing the Application Engine itself. The code in the configured and defined plug-in for the Application Engine being run is executed in place of the delivered code at runtime
There are a few things the development team should know prior to starting down the path of utilizing this functionality. One really nice feature of the AE Plug-in functionality is that developers are able to re-use the same SQL and PeopleCode multiple times for different Application Engine programs. Along with this, actions belonging to the same step of the same section of the App Engine can have multiple plug-in actions defined. On the flip-side, once an App Engine is configured to use a plug-in, it cannot be used as a plug-in for a different App Engine. Further, you cannot define a plug-in for an Application Engine action that has already been used by a different Application Engine as a plug-in. Bottom-line, no stacking plug-ins on top of plug-ins.
Clearly, this functionality is a further effort by Oracle to keep the core of PeopleSoft untouched while providing options and opportunities to allow development teams to provide the business with the specific functionality needed. These types of updates and improvements in the PeopleSoft architecture will allow for smoother upgrades and simpler retrofitting when required.
Linked Resource: Configuring Application Engine Action Plug-ins