Three-Tier Computing and Distributed Transactions

You can use SAP Sybase IQas a database server or resource manager, participating in distributed transactions coordinated by a transaction server.

A three-tier environment, where an application server sits between client applications and a set of resource managers, is a common distributed-transaction environment. Sybase EAServer and some other application servers are also transaction servers.

Sybase EAServer and Microsoft Transaction Server both use the Microsoft Distributed Transaction Coordinator (DTC) to coordinate transactions. SAP Sybase IQ provides support for distributed transactions controlled by the DTC service, so you can use SAP Sybase IQ with either of these application servers, or any other product based on the DTC model.

When integrating SAP Sybase IQ into a three-tier environment, most of the work needs to be done from the application server. This section provides an introduction to the concepts and architecture of three-tier computing, and an overview of relevant SAP Sybase IQ features. It does not describe how to configure your application server to work with SAP Sybase IQ. For more information, see your application server documentation.

• Three-Tier Computing Architecture
  In three-tier computing, application logic is held in an application server, such as Sybase EAServer, which sits between the resource manager and the client applications. In many situations, a single application server may access multiple resource managers. In the Internet case, client applications are browser-based, and the application server is generally a web server extension.
• Distributed Transactions
  While SAP Sybase IQ is enlisted in a distributed transaction, it hands transaction control over to the transaction server, and SAP Sybase IQ ensures that it does not perform any implicit transaction management. The following conditions are imposed automatically by SAP Sybase IQ when it participates in distributed transactions: