How to resolve ORA-04091 Error Message in Oracle database

Learn the reason and how to resolve the ORA-04091 error message in Oracle.

Description

When you encounter an ORA-04091 error, the following error message will appear:

ORA-04091: table name is mutating, trigger/function may now not see it

Cause

A assertion performed a trigger or customized PL/SQL function. That trigger/function tried to adjust or question a desk that is presently being modified with the aid of the declaration that fired the trigger/function.

Resolution

The option(s) to resolve this Oracle error are:

Option #1

Re-write the trigger/function so that it does no longer strive to modify/query the desk in question.

For example, if you’ve got created a trigger in opposition to the desk known as orders and then the set off performed a SELECT against the orders desk as follows:

CREATE OR REPLACE TRIGGER orders_after_insert
AFTER INSERT
   ON orders
   FOR EACH ROW

DECLARE
   v_quantity number;

BEGIN
   SELECT quantity
   INTO v_quantity
   FROM orders
   WHERE order_id = 1;

END;

You would receive an error message as follows:

When you create a set off against a table, you can’t modify/query that desk until the trigger/function has completed.

Remember that you can constantly use the :NEW and :OLD values inside the trigger, depending on the type of trigger. Learn more about Triggers.