Sometime we need to override EOImpl method to do some extra validation or other custom code.
One of most used overridden method is PostChanges() to intercept the logic before actually commit happens. This can be used to call PL/SQL method to push the Middle-Tier data without committing the changes.
As per Oracle documentation postChange Documentation , This method calls doDML with DML_INSERT , DML_UPDATE , DML_DELETE flags.
PostChanges() is called when all validation and custom validation is completed and you have data in entity cache which is validated , but about to be committed.
Most of the bloggers have suggested to use this method to call PL/SQL while migrating legacy application. Further research is advisable.