Microsoft® SQL Server® 2012 Bible

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Chapter 15: Executing Distributed Queries

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SET LastName = 'Klein'

WHERE ContactID = 55

UPDATE AvalonDev.AdventureWorks.Person.Contact

SET LastName = 'Klein'

WHERE ContactID = 55

COMMIT TRANSACTION

There is a difference between rolling back a local transaction and a DTC transaction.

Rolling back a nested SQL Server local transaction rolls back all the pending transactions.

DTC uses true nested transactions, and rolling back a DTC transaction can roll back only the

current transaction.

Monitoring Distributed Transactions

The Distributed Transaction Coordinator (see Figure 15-3) is a completely separate service

than SQL Server, and thus can be viewed from within the Windows operating system via

the Component Services application.

FIGURE 15-3

Distributed Transaction Coordinator.

Performance Consideration

In the beginning of this chapter, the following statement was made: “With SQL Server, get-

ting to and querying distributed data is not a problem; SQL Server can access data from a

plethora of data sources. SQL Server provides several methods for accessing data from many

different external data sources from a source location.” Yet, you cannot simply rely on dis-

tributed queries alone to solve complex application performance concerns.

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