2.3 When to Use Autonomous Transactions

Where would you find autonomous transactions useful in your applications? First, let's reinforce the general principle: you will want to define your program module as an autonomous transaction whenever you want to isolate the changes made in that module from the caller's transaction context.

Here are some specific ideas:

Logging mechanism

On the one hand, you need to log an error to your database log table. On the other hand, you need to roll back your core transaction because of the error. And you don't want to roll back over other log entries. What's a person to do? Go autonomous!

Commits and rollbacks in your database triggers

If you define a trigger as an autonomous transaction, then you can commit and/or roll back in that code. Developers have been asking for this capability for a long time.

Retry counter

Suppose that you want to let a user try to get access to a resource N times before an outright rejection; you also want to keep track of attempts between connections to the database. This persistence requires a COMMIT, but one that should remain independent of the transaction.

Software usage meter

You want to keep track of how often a program is called during an application session. This information is not dependent on, and cannot affect, the transaction being processed in the application.

Reusable application components

This usage goes to the heart of the value of autonomous transactions. As we move more thoroughly into the dispersed, multilayered world of the Internet, it becomes ever more important to be able to offer standalone units of work (also known as cartridges ) that get their job done without any side effects on the calling environment. Autonomous transactions will play a crucial role in this area.

Before we take a look at how you might use autonomous transactions for these scenarios, let's get a clearer picture about what you can and cannot do with autonomous transactions.