What are the characteristics of autonomous transactions?

Autonomous transaction defined and executedindependent of calling program.
u need to define PRAGMA AUTONOMOUS_TRANSACTION at declare section. stored procedure, function can be defined as autonomous transaction.

Autonomous transactions refer to the ability of PL/SQL temporarily suspend the current transaction and begin another transaction.  The second transaction is known as an autonomous transaction, and functions independently from the parent code.  This is especially important for PL/SQL exception handling, as we will see in a minute.

A PL/SQL autonomous transaction has the following characteristics:

The child code runs independently of its parent.
The child code can commit or rollback & parent resumes.
The parent code can continue without affecting child work