[DB] Complete Guide to Oracle ORA-06512 Error: Causes and Solutions

Complete Guide to Oracle ORA-06512 Error: Causes and Solutions

Overview

Hello! In this post, we'll take a detailed look at the ORA-06512 error, which is frequently encountered when using Oracle databases. This error can be somewhat confusing when developers and DBAs first encounter it, but it is essentially a message that provides very important information.

In this article, I'll explain in detail the exact meaning of the ORA-06512 error and how to effectively resolve it. From PL/SQL exception handling to actual debugging techniques, I'll cover everything you can apply directly in practice.

Table of Contents

1. What is ORA-06512 Error?

2. ORA-06512 Error Message Structure and Main Causes

3. Methods to Resolve ORA-06512 Error

4. Real-World Cases and Debugging Methods

5. Related Errors That Frequently Occur Together

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#1. What is ORA-06512 Error?

ORA-06512 is an error message that delivers call stack information when an exception occurs during PL/SQL code execution in Oracle databases. This error itself is not the cause of the problem, but rather a type of information delivery message that tells you where the problem occurred.

ORA-06512 typically occurs together with other Oracle error messages and tells you the exact location where the error occurred. In other words, this error plays the role of telling you "where" the problem occurred, not "what" the problem is.

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#2. ORA-06512 Error Message Structure and Main Causes

1) Error Message Structure

The ORA-06512 error message is displayed in the following structure:

ORA-06512: at "SCHEMA_NAME.PROCEDURE/FUNCTION_NAME", line LINE_NUMBER

Or:

ORA-06512: at line LINE_NUMBER

This message provides the following information:

① Schema name: The owner of the object where the error occurred
② Procedure/Function name: The PL/SQL code block (procedure, function, package, etc.) where the exception occurred
③ Line number: The exact line number within that code block where the error occurred

For example:

ORA-06512: at "HR.UPDATE_EMPLOYEE", line 45

This means an error occurred at line 45 of the UPDATE_EMPLOYEE procedure/function in the HR schema.

. . . . .

2) Main Causes of ORA-06512 Error

ORA-06512 itself is not the cause but a message that provides location information, so the actual cause of the problem should be found in the other error messages displayed with it. Generally, the error message that appears first in the error stack is the actual cause of the problem.

Main causes include the following cases:

① Explicit exception raising: When an exception is explicitly raised through a RAISE statement
② Predefined exceptions: When predefined exceptions such as NO_DATA_FOUND or TOO_MANY_ROWS occur
③ SQL errors: Errors that occur during SQL statement execution (table/column not found, constraint violations, etc.)
④ User-defined exceptions: When user-defined exceptions occur
⑤ Resource limitations: When resource limits such as insufficient memory or cursor count exceeded are reached
⑥ Nested procedure/function calls: Errors that occur in multiple layers of the call stack

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#3. Methods to Resolve ORA-06512 Error

The basic approach to resolving the ORA-06512 error is as follows:

1) Check the Actual Error Message

The first message in the error stack tells you the actual cause of the problem. For example:

ORA-01403: no data found
ORA-06512: at "HR.GET_EMPLOYEE", line 22
ORA-06512: at "HR.UPDATE_SALARY", line 15
ORA-06512: at line 3

Here, the actual problem is ORA-01403: no data found, meaning there is no data to retrieve.

. . . . .

2) Code Inspection

Check the code location mentioned in the error message:

-- Check the source code of the procedure
SELECT TEXT
FROM USER_SOURCE
WHERE NAME = 'UPDATE_EMPLOYEE'
ORDER BY LINE;

. . . . .

3) Add Exception Handling Logic

Add appropriate handling logic for possible exceptions:

CREATE OR REPLACE PROCEDURE update_employee(p_emp_id IN NUMBER) AS
BEGIN
  -- Existing code

  EXCEPTION
    WHEN NO_DATA_FOUND THEN
      -- Processing logic when data is not found
      DBMS_OUTPUT.PUT_LINE('Employee ID ' || p_emp_id || ' not found.');
    WHEN OTHERS THEN
      -- Other exception handling
      DBMS_OUTPUT.PUT_LINE('Error: ' || SQLERRM);
      -- Additional processing such as error logging
END;

. . . . .

4) Add Debugging Information

Add debugging information to identify the problem:

CREATE OR REPLACE PROCEDURE debug_proc AS
  v_var NUMBER;
BEGIN
  DBMS_OUTPUT.PUT_LINE('Starting procedure...');

  -- Before problematic section
  DBMS_OUTPUT.PUT_LINE('Before problematic section');

  -- Code that may cause problems
  SELECT salary INTO v_var FROM employees WHERE employee_id = 999;

  -- After problematic section (not executed if exception occurs)
  DBMS_OUTPUT.PUT_LINE('After problematic section');

EXCEPTION
  WHEN OTHERS THEN
    DBMS_OUTPUT.PUT_LINE('Error: ' || SQLERRM);
    DBMS_OUTPUT.PUT_LINE('Error stack: ' ||
                          DBMS_UTILITY.FORMAT_ERROR_STACK);
    DBMS_OUTPUT.PUT_LINE('Error backtrace: ' ||
                          DBMS_UTILITY.FORMAT_ERROR_BACKTRACE);
    RAISE; -- Optionally re-raise the exception
END;

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#4. Real-World Cases and Debugging Methods

Let's look at actual ORA-06512 error cases and effective debugging methods:

1) Case 1: NO_DATA_FOUND Exception in Stored Procedure

(1) Error Message

ORA-01403: no data found
ORA-06512: at "HR.GET_EMPLOYEE_SALARY", line 15

(2) Problem Code

CREATE OR REPLACE PROCEDURE get_employee_salary(
  p_emp_id IN NUMBER,
  p_salary OUT NUMBER
) AS
BEGIN
  SELECT salary INTO p_salary
  FROM employees
  WHERE employee_id = p_emp_id;
END;

(3) Solution

CREATE OR REPLACE PROCEDURE get_employee_salary(
  p_emp_id IN NUMBER,
  p_salary OUT NUMBER
) AS
BEGIN
  SELECT salary INTO p_salary
  FROM employees
  WHERE employee_id = p_emp_id;

EXCEPTION
  WHEN NO_DATA_FOUND THEN
    p_salary := NULL;
    -- Or log, raise user-defined exception, etc.
END;

. . . . .

2) Case 2: Exception in Trigger

(1) Error Message

ORA-00001: unique constraint violated
ORA-06512: at "HR.EMP_ID_CHECK_TRIGGER", line 5
ORA-04088: error during execution of trigger 'HR.EMP_ID_CHECK_TRIGGER'

(2) Problem Code and Solution

CREATE OR REPLACE TRIGGER emp_id_check_trigger
BEFORE INSERT ON employees
FOR EACH ROW
DECLARE
  v_count NUMBER;
BEGIN
  -- Check if already exists in audit table
  SELECT COUNT(*) INTO v_count
  FROM employee_audit
  WHERE employee_id = :new.employee_id
    AND action = 'INSERT';

  -- Insert only if it doesn't exist
  IF v_count = 0 THEN
    INSERT INTO employee_audit(
      employee_id, action_date, action
    )
    VALUES (:new.employee_id, SYSDATE, 'INSERT');
  END IF;
END;

. . . . .

3) Debugging Tip: Output Detailed Error Information

DECLARE
  v_error_stack VARCHAR2(4000);
  v_call_stack VARCHAR2(4000);
BEGIN
  -- Execute problem code

EXCEPTION
  WHEN OTHERS THEN
    v_error_stack := DBMS_UTILITY.FORMAT_ERROR_STACK;
    v_call_stack := DBMS_UTILITY.FORMAT_ERROR_BACKTRACE;

    -- Log error information
    INSERT INTO error_log (
      error_time, error_code, error_message,
      error_stack, call_stack, procedure_name
    ) VALUES (
      SYSTIMESTAMP, SQLCODE, SQLERRM,
      v_error_stack, v_call_stack, 'your_procedure_name'
    );

    RAISE;
END;

. . . . .

4) Debugging Tip: Section-by-Section Tracking

CREATE OR REPLACE PROCEDURE debug_sections AS
  v_section VARCHAR2(30);
BEGIN
  v_section := 'INITIALIZATION';
  DBMS_OUTPUT.PUT_LINE('Starting: ' || v_section);
  -- Initialization code

  v_section := 'DATA_RETRIEVAL';
  DBMS_OUTPUT.PUT_LINE('Starting: ' || v_section);
  -- Data retrieval code

  v_section := 'DATA_PROCESSING';
  DBMS_OUTPUT.PUT_LINE('Starting: ' || v_section);
  -- Data processing code

EXCEPTION
  WHEN OTHERS THEN
    DBMS_OUTPUT.PUT_LINE('Error in: ' || v_section);
    DBMS_OUTPUT.PUT_LINE('Error: ' || SQLERRM);
    RAISE;
END;

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#5. Related Errors That Frequently Occur Together

Let's look at errors that frequently occur together with ORA-06512 and their meanings:

1) ORA-01403: no data found

① When data is not found in a SELECT INTO statement
② Solution: Check data existence or add exception handling

. . . . .

2) ORA-01422: exact fetch returns more than requested number of rows

① When multiple rows are returned in a SELECT INTO statement
② Solution: Make WHERE condition more specific or use CURSOR

. . . . .

3) ORA-00001: unique constraint violated

① Unique constraint violation
② Solution: Add duplicate data check logic

. . . . .

4) ORA-04068: existing state of packages has been discarded

① When previous state is invalidated after package recompilation
② Solution: Reconnect session or review package initialization logic

. . . . .

5) ORA-06502: PL/SQL: numeric or value error

① Numeric operation error or variable size limit exceeded
② Solution: Adjust data type and size

. . . . .

6) ORA-06511: PL/SQL: cursor already open

① Attempting to open an already open cursor
② Solution: Review cursor management logic

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Conclusion

The ORA-06512 error is not an error that causes problems by itself, but rather a message that tells you where the problem occurred. To effectively handle this error:

① Check other error messages that occurred together to identify the actual cause.
② Confirm the exact location (procedure/function and line number) where the error occurred.
③ Add appropriate exception handling logic to deal with predictable exception situations.
④ Use logging and debugging information to track the path where the problem occurred.

In PL/SQL development, the ORA-06512 error message ultimately provides important clues that become the starting point for problem resolution. If you correctly interpret and utilize the information provided by this error message, you'll be able to solve problems quickly and accurately even in complex PL/SQL applications.

I hope this guide will be helpful when developing or maintaining PL/SQL code in your work. When problems occur, calmly analyze the error stack and use appropriate debugging techniques to effectively resolve issues.

Thank you for reading this long article.

The end.