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PLS-00306: Wrong Number or Types of Arguments in Call To – Explained with Solutions

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PLS-00306: Wrong Number or Types of Arguments in Call To – Explained with Solutions

If you’re working with Oracle PL/SQL and you’ve come across the PLS-00306 error, you’re not alone. This error is one of the most common issues developers face when calling procedures, functions, or packages. It can be a little frustrating at first, but the good news is — it’s usually easy to fix once you understand what’s causing it.

In this detailed guide from MagazineBlogs.co.uk, we’ll break down exactly what PLS-00306 means, why it happens, and how to troubleshoot and fix it effectively.

📌 What is PLS-00306?

PLS-00306: mismatched or incorrect number of parameters supplied in function or procedure call
This Oracle error occurs when you’re trying to call a procedure, function, or package with the wrong number of arguments or with arguments of the wrong data type.

🧠 Why Does It Happen?

There are two primary reasons this error is raised:

  1. The number of parameters doesn’t match what the procedure or function expects.

  2. The data types of the parameters are incorrect or mismatched with the expected signature.

This happens commonly when:

  • You change the procedure’s signature but forget to update all the places it’s called.

  • You’re calling built-in packages like DBMS_SQL, UTL_HTTP, etc., with incorrect arguments.

  • The overload resolution fails (when multiple procedures with the same name exist, and the compiler can’t decide which one to use).

🔍 Common Scenario That Triggers PLS-00306

Here’s a simple example:

plsql
-- Procedure definition
CREATE OR REPLACE PROCEDURE greet_user(name IN VARCHAR2, age IN NUMBER) IS
BEGIN
DBMS_OUTPUT.PUT_LINE('Hello ' || name || ', Age: ' || age);
END;

Calling it like this:

plsql
BEGIN
greet_user('Alice'); -- Missing the second argument
END;

Will raise:

pgsql
PLS-00306: wrong number or types of arguments in call to 'GREET_USER'

✅ How to Fix PLS-00306

Here are practical steps to resolve the issue:

1. Check the Procedure/Function Signature

Always check the number and types of parameters the procedure or function expects.

sql
-- Use this to inspect the procedure:
SELECT argument_name, position, data_type, in_out
FROM all_arguments
WHERE object_name = 'GREET_USER'
AND owner = 'YOUR_SCHEMA'
ORDER BY position;

2. Match the Parameters Exactly

Make sure:

  • The number of arguments matches.

  • The order of parameters is correct.

  • The data types are compatible (e.g., don’t pass VARCHAR2 to a NUMBER parameter).

3. Check for Overloaded Procedures

If multiple procedures with the same name exist (overloading), ensure you’re calling the correct one.

Oracle supports overloading, but it can be tricky. Example:

plsql
-- Two procedures with same name but different signatures
PROCEDURE add_employee(name IN VARCHAR2);
PROCEDURE add_employee(name IN VARCHAR2, dept_id IN NUMBER);

Calling it with just one parameter should match the first one. If types are off even slightly (e.g., passing a CHAR when it expects VARCHAR2), it can still throw PLS-00306.

4. PL/SQL Anonymous Block Mistakes

Sometimes the error comes from calling a procedure within an anonymous block or from a different session that doesn’t “see” the latest version of the procedure. In such cases:

  • Recompile the procedure using ALTER PROCEDURE ... COMPILE;

  • Clear session cache or reconnect to avoid version mismatches

5. Using Named Parameters (Optional but Helpful)

Named parameters can help prevent mismatch errors:

plsql
BEGIN
greet_user(name => 'Alice', age => 30);
END;

This also improves readability and reduces the chance of type/order-related errors.

🛠️ Debugging Tips

  • Use DBMS_OUTPUT or logging to identify the exact values and types being passed.

  • Use %TYPE in your declarations to match variable types with database columns or procedure arguments.

  • Compile your packages/procedures with SHOW ERRORS; to catch any signature mismatches early.

⚠️ PLS-00306 with Built-In Packages

You may also encounter this error when using built-in Oracle packages like:

  • DBMS_SQL

  • UTL_FILE

  • DBMS_LOB

In these cases, double-check the Oracle documentation for the correct syntax and supported argument types, especially after a database version upgrade.

📚 Final Thoughts

The PLS-00306 error in Oracle PL/SQL is a parameter mismatch issue — and while it’s one of the most common PL/SQL errors, it’s also one of the most easily fixable. A careful review of your procedure/function signatures, along with correct parameter usage, will resolve the error in almost all cases.

If you’re developing complex PL/SQL applications, using tools like TOAD, SQL Developer, or PL/SQL Developer can help you auto-check parameter types and signatures, reducing the chance of these errors.

💬 Have you faced this error in a different context? Drop your story in the comments below and let’s debug together!

📌 Stay tuned to MagazineBlogs.co.uk for more developer-friendly tutorials and troubleshooting guides.

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