---
title: "Transaction Promotion | Microsoft Docs"
ms.custom: ""
ms.date: "03/14/2017"
ms.prod: sql
ms.reviewer: ""
ms.technology: clr
ms.topic: "reference"
helpviewer_keywords: 
  - "distributed transactions [CLR integration]"
  - "promoting transactions [CLR integration]"
  - "Enlist keyword"
  - "transaction promotion [CLR integration]"
ms.assetid: 5bc7e26e-28ad-4198-a40d-8b2c648ba304
author: "rothja"
ms.author: "jroth"
---
# Transaction Promotion
[!INCLUDE[appliesto-ss-xxxx-xxxx-xxx-md](../../includes/appliesto-ss-xxxx-xxxx-xxx-md.md)]
  Transaction *promotion* describes a lightweight, local transaction that can be automatically promoted to a fully distributable transaction as needed. When a managed stored procedure is invoked within a database transaction on the server, the common language runtime (CLR) code is run in the context of a local transaction.  If a connection to a remote server is opened within a database transaction, the connection to the remote server is enlisted into the distributed transaction and the local transaction is automatically promoted to a distributed transaction. So, transaction promotion minimizes the overhead of distributed transactions by deferring the creation of a distributed transaction until it is needed. Transaction promotion is automatic, if it has been enabled using the **Enlist** keyword, and does not require intervention from the developer. The .NET Framework Data Provider for [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] provides support for transaction promotion, handled through the classes in the .NET Framework **System.Data.SqlClient** namespace.  
  
## The Enlist Keyword  
 The **ConnectionString** property of a **SqlConnection** object supports the **Enlist** keyword, which indicates whether **System.Data.SqlClient** detects transactional contexts and automatically enlists the connection in a distributed transaction. If this keyword is set to true (the default), the connection is automatically enlisted in the current transaction context of the opening thread. If this keyword is set to false, the SqlClient connection does not interact with a distributed transaction. If **Enlist** is not specified in the connection string, the connection is automatically enlisted in a distributed transaction if one is detected at the time the connection is opened.  
  
## Distributed Transactions  
 Distributed transactions typically consume significant system resources. [!INCLUDE[msCoName](../../includes/msconame-md.md)] Distributed Transaction Coordinator (MS DTC) manages such transactions, and integrates all of the resource managers accessed in these transactions. Transaction promotion, on the other hand, is a special form of a **System.Transactions** transaction that effectively delegates the work to a simple [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] transaction. **System.Transactions**, **System.Data.SqlClient**, and [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] coordinate the work involved in handling the transaction, promoting it to a full distributed transaction as needed.  
  
 The benefit of using transaction promotion is that when a connection is opened with an active **TransactionScope** transaction, and no other connections are opened, the transaction commits as a lightweight transaction, rather than incurring the additional overhead of a full distributed transaction. For more information about **TransactionScope**, see [Using System.Transactions](../../relational-databases/clr-integration-data-access-transactions/using-system-transactions.md).  
  
## See Also  
 [CLR Integration and Transactions](../../relational-databases/clr-integration-data-access-transactions/clr-integration-and-transactions.md)