ORA-06512 is often misunderstood as the primary cause of an Oracle error, when in reality it just pinpoints where an exception occurred in your PL/SQL code. The true issue usually lies in a preceding error, such as an unhandled exception or data mismatch, hidden earlier in the stack. 

In contrary to ORA-12154 or ORA-00600—which typically point to direct connectivity or internal database failures—ORA-06512 simply acts as a line-number reference. It tells you where an error occurred, not why.

What Is ORA-06512?

ORA-06512 is an Oracle error that indicates the line number within a PL/SQL code block or stored procedure where an exception occurred. On its own, it does not tell you the actual cause of the error; it merely pinpoints where in the code stack the exception happened. To identify the true reason for the failure, you need to look at preceding errors in the stack (for example, ORA-06502 for numeric or value errors).

This error typically shows up in two parts of the stack trace:

• At “SCHEMA.PROCEDURE_NAME”, line X – Pinpoints the exact line in the PL/SQL unit.
• At line Y – Indicates the line in the calling context or in an anonymous PL/SQL block.

Common Causes of ORA-06512

ORA-06512 can arise from multiple issues in a PL/SQL environment, but three categories of problems are especially common.

Unhandled Exceptions

When your PL/SQL code encounters a situation outside normal processing—such as a division by zero, numeric overflow, or a user-defined condition—it raises an exception. If that exception is not caught by an EXCEPTION block, Oracle will unwind the stack and display ORA-06512 to report where it happened. User-defined exceptions (using RAISE) and system exceptions (like ORA-06502) alike can cause this outcome if they remain unhandled.

Data Type Issues

A common culprit is data type mismatch, such as:

• Assigning a 3-digit value to a variable declared as NUMBER(2).
• Storing a string that exceeds the length limit of a VARCHAR2 column.

These problems trigger runtime exceptions, which in turn produce ORA-06512 messages referring to the line where the incompatible assignment occurred.

Code/Logic Errors

Other coding mistakes can also raise exceptions unexpectedly:

• Referencing a variable that has not been properly initialized.
• Looping conditions that attempt operations on nonexistent data.
• Calling a procedure that expects different parameters than what is actually passed.

All of these scenarios can result in Oracle throwing an exception, displaying ORA-06512, and halting the process unless there is an appropriate exception handler in place.

How to Diagnose ORA-06512

Figuring out why ORA-06512 appears often requires looking beyond the number in the error message. 

Reading the Full Error Stack

Because ORA-06512 only shows the line in your PL/SQL unit where an exception occurred, the real cause typically appears in preceding errors. For instance, you might see something like:

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

ORA-06512: at “SCHEMA.PROCEDURE_NAME”, line 5

ORA-06512: at line 1

Here, the first error (ORA-06502) points to a numeric or value error, while ORA-06512 clarifies the location of that error. Always review the full error stack to determine the primary issue.

Checking Related Code or Triggers

If the main code looks correct, examine triggers or nested procedures that might indirectly cause an exception. For example, a BEFORE UPDATE trigger on the same table could loop back and try to update the row it just received, leading to a recursive call or a data mismatch error. Review any dependencies or triggers that handle the same tables and columns referenced in your procedure.

Strategies to Resolve ORA-06512

Once you have identified the root issue—whether it’s a type mismatch, a logic error, or an unhandled exception—the next step is to apply targeted solutions. 

Fix the Underlying Error

The first and most direct solution is to address the root cause of the exception itself:

• Match Data Types Properly: Increase numeric precision if you need to handle larger values. Ensure VARCHAR2 fields can store the maximum length of data you plan to insert.
• Repair Logic Mistakes: Double-check the code flow for invalid operations. If a procedure expects a certain parameter type or range, verify you’re passing valid arguments.
• Correct Any SQL Statements: Confirm that your table definitions match the insert or update statements. If a table has a column NUMBER(10,0), don’t pass in longer or incompatible values.

Use Exception Handlers

If simply fixing the root issue is not enough—or if you need more granular control—you should add EXCEPTION blocks to handle errors gracefully. An EXCEPTION block allows you to catch specific errors (like NO_DATA_FOUND or TOO_MANY_ROWS) or to use a WHEN OTHERS THEN clause for unexpected conditions. Handling exceptions in your PL/SQL code helps you perform clean-up tasks, log error details, or assign fallback values when something goes wrong, rather than letting Oracle terminate the process and produce an ORA-06512 message.

Here’s a basic example:

BEGIN

   — Some operation that might fail

   SELECT total INTO v_total FROM sales WHERE …

EXCEPTION

   WHEN NO_DATA_FOUND THEN

      — Handle the case where the query returns no rows

      v_total := 0;

   WHEN OTHERS THEN

      — Catch any other exceptions

      RAISE_APPLICATION_ERROR(-20001, ‘Unexpected Error Occurred’);

END;

In this scenario, you’re preventing uncaught exceptions from bubbling up and causing a vague ORA-06512 message. Instead, you control how the process reacts and what users see as an error message or fallback behavior.

Raise Custom Errors Appropriately

Using custom error messages can clarify the root issue for anyone troubleshooting the application. Rather than relying on Oracle’s default messages, you can call RAISE_APPLICATION_ERROR with a custom code and descriptive text:

Copy code

DECLARE

   v_number NUMBER(2);

BEGIN

   v_number := 100; — This is too large for NUMBER(2)

EXCEPTION

   WHEN VALUE_ERROR THEN

      RAISE_APPLICATION_ERROR(

         -20002,

         ‘Attempted to store a 3-digit value in a 2-digit field.’

      );

END;

This approach makes it clear what went wrong and why, instead of producing a stack trace that only shows ORA-06512 and a generic numeric error.