DTC Administration Guide

Component PSDK

You can administer distributed transactions through the Microsoft Distributed Transaction Coordinator (DTC), which is included with the Component Services administrative tool. The DTC provides services designed to ensure successful and complete transactions, even with system failures, process failures, and communication failures. For step-by-step instructions on how to perform specific DTC administrative tasks, see the Help documentation for the Component Services administrative tool on your system.

Note:
When a transaction updates data on more than one networked computer, it is called a distributed transaction. Many aspects of a distributed transaction are identical to a transaction whose scope is a single database. For example, a distributed transaction provides predictable behavior by enforcing the ACID properties that define all transactions.

Each computer participating in a distributed transaction manages its own resources and data and also acts in concert with other computers in the transaction. Above all, a distributed transaction must commit or abort its work entirely on all participating computers. The DTC performs the transaction coordination role for the components involved and acts as a transaction manager for each computer that manages transactions.

Acting as a transaction processing monitor, COM+ reduces the complications associated with distributed transactions. For example, through the DTC, COM+ uses the OLE Transactions protocol to coordinate transactions that span multiple networked computers. COM+ also supports transaction coordination by X/OPEN XA-compliant transaction managers.

The DTC uses the two-phase commit protocol. Phase one involves the transaction manager requesting each enlisted component to prepare to commit; in phase two, if all enlistees successfully prepare, the transaction manager broadcasts the commit decision.

In general, transactions involve the following steps:

Applications call the transaction manager to begin a transaction.
When the application has prepared its changes, it asks the transaction manager to commit the transaction. The transaction manager keeps a sequential transaction log so that its commit or abort decisions will be durable.
- If all components are prepared, the transaction manager commits the transaction and the log is cleared.
- If any component cannot prepare, the transaction manager broadcasts an abort decision to all elements involved in the transaction.
- While a component remains prepared but not committed or aborted, it is in doubt about whether the transaction committed or aborted. If a component or transaction manager fails, it reconciles in-doubt transactions when it reconnects.

See the topics described in the following table for background information about specific DTC administration topics.

Topic	Description
DTC Components	Describes DTC components and how to configure them within your network.
DTC Security Considerations	Overview of available options for configuring security for the DTC.
DTC Configuration Overview	Overview of available options for configuring the DTC for your particular network needs.
DTC Log File Management	Overview of streamlining performance by managing the transaction log file.
DTC Transaction States	Overview of transaction states and transaction resolution after a system failure.
Managing XA Transactions	Overview of using the DTC Transaction List to manage XA-compliant transactions.
Managing IBM CICS LU 6.2 Transactions	Overview of how the DTC works with IBM systems that support the IBM LU 6.2 protocol.
Using the DTC Transaction List and Transaction Properties Windows	Overview of how to use the Transaction List and Transaction Properties windows in the Component Services administrative tool.
DTC Transaction Statistics Window Contents	Overview of how to use the Transaction Statistics window in the Component Services administrative tool.