The installation process for the Application Server role provides an option for enabling the Distributed Transaction Coordinator (DTC). When you enable the DTC, Application Server automatically configures the DTC to allow network transactions. Application Server also creates a firewall rule that allows network traffic to pass to and from the DTC.
In information processing, a transaction is a series of operations that are treated as a single, atomic unit—all of the operations occur, or none of them occur. For example, a series of insert and update operations on a database might be committed as a transaction. In situations in which a transaction involves only a single resource, the resource manager itself (in this case, the database) can manage the entire transaction. In some situations, the operations in a transaction update data on multiple networked computers. This is called a distributed transaction. The DTC in Windows Server 2008 can coordinate the updates as a single transaction across resources that span multiple networked computers. For more information about the DTC, see Distributed Transaction Coordinator (
Application Server does not enable distributed transaction support by default. Ensure that the Application Server role is installed with the DTC option enabled on every server that hosts an application or a resource that will participate in the distributed transaction. These applications and resources can include an application that creates distributed transactions, an application that can participate in distributed transactions (such as a transactional COM+ component), and a resource (such as a database) that can participate in distributed transactions.
When you install the Application Server role, you can install the Distributed Transactions service with the following options:
Incoming Remote Transactions: In some situations, a distributed transaction is initiated on a remote computer, and an operation within the transaction involves a resource on the local computer. In this situation, we say that the transaction "flows into" the local computer and that the local resource (for example, a database) "enlists" in the transaction that was initiated on the remote computer. Enabling this option provides distributed transaction support for applications that enlist in remote transactions.
Outgoing Remote Transactions: In some situations, a local application initiates a transaction and performs update operations on resources that are located on remote computers. In this situation, we say that the transaction "flows out" of the local computer and is "propagated" to a resource on the remote computer. Enabling this option provides distributed transaction support for the outward propagation of transactions.
WS-Atomic Transaction Support: This option provides distributed transaction support for applications that use the Simple Object Access Protocol (SOAP) and the WS-Atomic Transaction standard for communication and transaction coordination.