In Oracle E-Business Suite 11.5.x, PL/SQL packages owned by APPS were created with invoker rights, resulting in the execution of the program units with the privileges of the caller. However, with R12, Oracle changed the package security model to definer rights. Privileges of the package owner, also known as the definer, are used at execution time.
The fact that definer rights not only dictate the privileges, but also are used to resolve object references, prevents the seamless data access layer from functioning correctly. Customers therefore need to download and apply Oracle Patch 9015132 "ENABLING INVOKERS PROCESSING IN R12" to revert the package security model back to invoker rights.