Here is the abstract of a talk given by a former PL/SQL product manager on this topic:
“Large software systems must be built from modules. A module hides its implementation behind an interface that exposes its functionality. This is computer science’s most famous principle. For applications that use an Oracle Database, the database is, of course, one of the modules. The implementation details are the tables and the SQL statements that manipulate them. These are hidden behind a PL/SQL interface. This is the Thick Database paradigm: select, insert, update, delete, merge, commit, and rollback are issued only from database PL/SQL. Developers and end-users of applications built this way are happy with their correctness, maintainability, security, and performance. But when developers follow the NoPlsql paradigm, their applications have problems in each of these areas and end-users suffer. This session provides PL/SQL devotees with unassailable arguments to defend their beliefs against attacks from skeptics; skeptics who attend will see the light.”
Here is a whitepaper that gives a careful and detailed account of what the presentation addresses.