In Oracle PL/SQL, what are PL/SQL subprograms (procedures and functions), and what are the main advantages of using them in database applications?

Introduction / Context:
PL/SQL is Oracle's procedural extension to SQL and allows developers to write complex logic close to the data in the database. Central to PL/SQL programming are subprograms, which include procedures and functions. These subprograms help structure code and can be stored in the database for repeated use. This question explores what PL/SQL subprograms are and why they are beneficial in enterprise applications.

Given Data / Assumptions:

• The database platform is Oracle, and the language is PL/SQL.
• Subprograms include stored procedures and stored functions.
• We want to identify both their nature and their advantages.
• We assume typical use in data centric applications.

Concept / Approach:
A PL/SQL subprogram is a named PL/SQL block that is stored in the database and can be called by name from other PL/SQL code, SQL statements, or client applications. Procedures perform actions and may or may not return values through parameters, while functions compute and return a single value. The advantages of subprograms include code reuse, better modular design, consistent business rules, centralized security, and potential performance improvements because the code is compiled and executed close to the data.

Step-by-Step Solution:
1. Recognize that subprograms are named units of PL/SQL code that can be defined once and invoked many times. 2. Understand the distinction between procedures, which generally do work, and functions, which return a value that can appear in expressions. 3. Note that storing logic in the database promotes reusability, because multiple applications and users can call the same subprogram. 4. Realize that centralizing business rules in subprograms can enforce consistency and simplify maintenance when rules change. 5. Consider that executing logic near the data can reduce network traffic and improve performance, since less data must be moved to the client.

Verification / Alternative check:
You can verify the nature of subprograms by creating a simple stored procedure or function and then calling it from various contexts, such as another PL/SQL block or a SQL statement for functions. You will see that the same subprogram executes consistently and that changes made in its definition automatically apply to all callers. Execution plans and performance measurements often show reduced latency when logic is pushed into well designed subprograms instead of being implemented entirely in application code.

Why Other Options Are Wrong:

• Option B is wrong because temporary tables hold data, not code; they are unrelated to subprogram logic.
• Option C is wrong because PL/SQL code runs inside the database engine, not in the browser; client side scripts are written in languages such as JavaScript.
• Option D is wrong because database startup is controlled by parameter files and services, not by PL/SQL subprograms.

Common Pitfalls:
Common mistakes include writing very large monolithic subprograms instead of breaking logic into smaller units, which reduces readability and reuse. Another pitfall is embedding too much business logic in client applications and not leveraging subprograms, which can lead to duplicated rules and inconsistent behaviour. Developers should design subprograms with clear interfaces, handle exceptions properly, and document their purpose so that other team members can use them correctly.

Final Answer:
The correct description is PL/SQL subprograms are named blocks of code such as procedures and functions that encapsulate logic for reuse, better modularity, improved security, and performance through stored execution, because this captures what subprograms are and why they are valuable in database applications.