COM & .NET Component Services

Transaction Properties

Modern standards call for a transaction to be atomic, consistent, isolated, and durable. In transaction processing terminology, these properties are referred to as the ACID properties. When you design transactional components, you must adhere to the ACID requirements; they are not optional. As you will see, COM+ enforces them rigorously. Once you understand the ACID requirements and follow simple design guidelines, developing transactional components in COM+ becomes straightforward.

The Atomic Property

When a transaction completes, all the changes it made to the system’s state must be made as if they were all one atomic operation. The word atom comes from the Greek word atomos, meaning indivisible. The changes made to the system are made as if everything else in the universe stops, the changes are made, and then everything resumes. It is not possible to observe the system with only some of the changes.

A transaction is allowed to change the system state only if all the participating objects and resources execute their part successfully. Changing the system state by making the changes is called committing the transaction. If any object encounters an error executing its part, the transaction aborts and none of the changes is committed. This process is called aborting the transaction. Committing or aborting a transaction must be done as an atomic operation.

A transaction should not leave things to do in the background once it is done, since those operations ...