In Oracle PL/SQL, how can you generate debugging output from a PL/SQL block so that you can inspect messages during development?

Introduction / Context:
Debugging PL/SQL code is an essential skill for database developers and DBAs. While advanced tools provide graphical debuggers, a very common and simple technique is to print messages from within PL/SQL blocks. Oracle provides the DBMS_OUTPUT package for this purpose. Understanding how to use DBMS_OUTPUT.PUT_LINE is a frequent interview topic because it demonstrates familiarity with basic diagnostic techniques in PL/SQL programming.

Given Data / Assumptions:
• The language in use is Oracle PL/SQL. • We want to generate human readable messages from within PL/SQL blocks during development. • We assume that the client tool (such as SQL*Plus or SQL Developer) has server output enabled. • No numeric computation is required; the focus is on the debugging facility.

Concept / Approach:
The DBMS_OUTPUT package contains procedures that allow PL/SQL code to place text into an output buffer on the server. The most commonly used procedure is DBMS_OUTPUT.PUT_LINE, which appends a line of text. When server output is enabled on the client (for example, by using SET SERVEROUTPUT ON in SQL*Plus), these lines are displayed after the PL/SQL block finishes. This method is simple and widely supported, making it a standard answer to the question of generating debugging output inside PL/SQL code. Other statements like ROLLBACK, SHUTDOWN, or GRANT are unrelated to diagnostic printing.

Step-by-Step Solution:
Step 1: Recall that Oracle provides a standard package called DBMS_OUTPUT for sending text messages from PL/SQL to the client. Step 2: Identify PUT_LINE as the procedure inside DBMS_OUTPUT that writes a single line of text followed by a newline character. Step 3: Understand that you can call DBMS_OUTPUT.PUT_LINE many times in a block to track variable values and program flow. Step 4: Remember that for messages to be visible, the client must enable server output. Step 5: Choose the option that explicitly mentions using DBMS_OUTPUT.PUT_LINE to print debugging messages.

Verification / Alternative check:
Imagine a simple example: BEGIN DBMS_OUTPUT.PUT_LINE('Debug: value of x = ' || x); END;. After running this block with server output enabled, you see the line Debug: value of x = 10 in your client tool. This is exactly the behavior interviewers expect you to describe. None of the other commands mentioned in the options are designed to produce line oriented debug output. ROLLBACK cancels transactions, SHUTDOWN stops the instance, and GRANT manages privileges, none of which are debugging tools. Therefore, DBMS_OUTPUT.PUT_LINE is the correct and standard way to generate simple debugging output from PL/SQL code.

Why Other Options Are Wrong:
Option b uses ROLLBACK, which undoes database changes but does not print any messages by itself. Option c suggests shutting down the database and reading alert logs, which is extreme and not appropriate for routine PL/SQL debugging. Option d uses GRANT to modify privileges, which is a security operation, not a debugging method. Option e falsely claims that debugging output is impossible, which ignores the existence of DBMS_OUTPUT and other debugging tools.

Common Pitfalls:
A common pitfall is forgetting to enable server output in the client, which makes it seem like DBMS_OUTPUT.PUT_LINE does nothing. Another mistake is relying solely on DBMS_OUTPUT in production code, which can clutter logs or slow down execution if overused. Developers should also distinguish between DBMS_OUTPUT messages and error messages generated by exceptions; the former are purely informational. For more advanced debugging, Oracle provides dedicated debuggers, but knowing DBMS_OUTPUT remains useful, especially in scripted or simple environments.

Final Answer:
The correct choice is Use the built-in DBMS_OUTPUT.PUT_LINE procedure to print messages to the output buffer., because DBMS_OUTPUT is the standard Oracle package for generating simple debugging output from within PL/SQL blocks.