http://msdn.microsoft.com/en-us/library/cc309178.aspx
Enterprise Library 3.1 - May 2007
Using the TransactionScope Class
Here are some partial quotes, but you should read the whole thing.
There have been changes to some of the Database class methods in order to
take advantage of the .NET Framework 2.0 TransactionScope class. This class
automatically enlists database calls into an ambient transaction.
If there are multiple connections, the TransactionScope class considers the
transaction to be a distributed transaction. Distributed transactions have a
significant performance and resource overhead compared with a local
transaction.
There is a 4.0 and 4.1 EnterpriseLibrary version as well.
