4.0.0 HP PolyServe Software for Microsoft SQL Server Administration Guide (T5392-96056, March 2010)

B Hosting Configurations for MS DTC
The information in this appendix applies to MS DTC when it is managed by a Virtual SQL Server (the
“Manage msdtc” option is enabled in the Virtual SQL Server configuration). If you are configuring
MS DTC for high availability, as described in Chapter 4, refer to that chapter for MS DTC configuration
information.
Overview
The information in this appendix applies to MS DTC when it is managed by a Virtual SQL Server (the
“Manage msdtc” option is enabled in the Virtual SQL Server configuration). If you are configuring
MS DTC for high availability, as described in Chapter 5, refer to that chapter for MS DTC configuration
information. Overview The Microsoft Distributed Transaction Coordinator (MS DTC) is the transaction
manager responsible for coordinating transaction atomicity across multiple resource managers. It
ensures that an update of data (work) is either committed or rolled back on all servers that are
participating in the transaction. As shown below, the client connects to Server A and invokes a remote
call to Server B, which employs MS DTC to manage the transaction across these two servers. With
the help of DTC, the work is guaranteed to either commit or rollback on both servers.
HP PolyServe Software for Microsoft SQL Server utilizes the PSFS cluster filesystem, in which all nodes
in the cluster can simultaneously read/write to a file on the shared disk. On failover, the backup node
simply starts up SQL Server and mounts the data on the shared disk. There is relatively little cost in
transition or data movement.
Whether SQL Server is running as stand-alone or clustered, MS DTC is needed if SQL Server (or
Virtual SQL Server) needs to maintain a transaction spanning across multiple data sources. Although,
as shown in the following section, HP PolyServe Software can transparently virtualize DTC service on
the active node (this option is enabled by checking the MSDTC checkbox), only one DTC-enabled
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