AUTONOMOUS_TRANSACTION Pragma

One of the questioned asked today about the limitation of autonomous_trasaction pragma (10gR2). 
PRAGMA
Signifies that the statement is a pragma (compiler directive). Pragmas are processed at compile time, not at run time. They pass information to the compiler.
You can apply this pragma to:

Top-level (not nested) anonymous PL/SQL blocks
 Local, standalone, and packaged functions and procedures
Methods of a SQL object type
Database triggers

You cannot apply this pragma to an entire package or an entire an object type. Instead, you can apply the pragma to each packaged subprogram or object method.
You can code the pragma anywhere in the declarative section. For readability, code the pragma at the top of the section.
Once started, an autonomous transaction is fully independent. It shares no locks, resources, or commit-dependencies with the main transaction. You can log events, increment retry counters, and so on, even if the main transaction rolls back.

Unlike regular triggers, autonomous triggers can contain transaction control statements such as COMMIT and ROLLBACK, and can issue DDL statements (such as CREATE and DROP) through the EXECUTE IMMEDIATE statement.

In the main transaction, rolling back to a savepoint located before the call to the autonomous subprogram does not roll back the autonomous transaction. Remember, autonomous transactions are fully independent of the main transaction.

If an autonomous transaction attempts to access a resource held by the main transaction (which cannot resume until the autonomous routine exits), a deadlock can occur. Oracle raises an exception in the autonomous transaction, which is rolled back if the exception goes unhandled.

If you try to exit an active autonomous transaction without committing or rolling back, Oracle raises an exception. If the exception goes unhandled, or if the transaction ends because of some other unhandled exception, the transaction is rolled back.

Example:

CREATE TABLE emp_audit ( emp_audit_id NUMBER(6), up_date DATE, 
                         new_sal NUMBER(8,2), old_sal NUMBER(8,2) );

CREATE OR REPLACE TRIGGER audit_sal
   AFTER UPDATE OF salary ON employees FOR EACH ROW
DECLARE 
   PRAGMA AUTONOMOUS_TRANSACTION;
BEGIN
-- bind variables are used here for values
   INSERT INTO emp_audit VALUES( :old.employee_id, SYSDATE, 
                                 :new.salary, :old.salary );
  COMMIT;
END;

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