Autonomous Transactions

Transactions are at the heart of any database management system. Autonomous transaction is a transaction that starts from a parent transaction but proceeds without any regard to the parent transaction. The typical application of autonomous transaction is of logging activity. If you want your logging activity to start on a certain event and then proceed without any regard to the activity for which the logging is taking place then the autonomous transactions are the natural solution. Oracle provides a very simple way to start an autonomous transaction. You can start an autonomous transaction in a PL/SQL block by including the "Pragma Autonomous Transaction" in the declarative section of the block. After the transaction has been started it will operate independently of the parent transaction. It does not rely on the success or failure of PL/SQL block from which it was started.

Talking about transactions; they operate without any user interaction. However Oracle allows you to have some control over their operation. The command "Set Transaction" is used to set five different arguments that will guide the transaction in its operation. The "Read only" argument makes the transaction to work only on a snapshot of data from the database. The "Read Write" argument will bring back the transaction to its default mode. The argument "Read Committed" specifies that if a user is updating a row of table and another user tries to do the same then the second user's transaction will wait for the first one's to complete. This is also the default behavior. The argument "Serializable" is almost the same as "Read Committed" except when set then the transaction of the second user will abort with an error. You can also name the rollback segment that the transaction should use while it proceeds with the argument "Rollback Segment". But remember before you do all this that the Command "Set Transaction" should be the first one in your transaction.