If you are planning an upgrade to R12 and wondering about all the ways it will affect you customizations, the following three tools will make your life easier. You can check all the components which have changed between the releases allowing you to manage your customiszations during the upgrade.
EBS File Comparison Report: Provides detailed information about what files were added, removed, or stubbed (made inactive) during changes between Releases 22.214.171.124 and 12.1.3 of Oracle E-Business Suite. It allows you to drilldown into the files(provided they are text-based) and view the differences between the two versions. It can be downloaded from Metalink Note#1446430.1.
EBS Data Model Comparison Report: Provides the database object definition changes between two EBS releases. This includes information regarding which objects were added, deleted and modified. In case of modified objects, it lists the actual changes made to the objects. This one is more useful than the previous one in the sense that it lists differences between 12.1.3 and all other releases from 11.5.9 onwards. The report can be downloaded from Metalink Note#1290886.1 .
EBS ATG Seed Date Comparison Report: Provides details on the changes between different EBS releases based upon the seed data changes delivered by the product data loader files (.ldt extension) based on EBS ATG loader control (.lct extension) files. This report list differences between 12.1.3 and all other releases from 126.96.36.199 onwards. It can be downloaded from Metalink Note#1327399.1.
The EBS Release Management Team deserves a shout out for this one.