Use iSeries Access for Windows in a three-tier environment

A wide variety of client workstations can access iSeries services through iSeries Access for Windows functions when the product is installed on the middle tier of a three-tier environment.

Additionally, three-tier environments present several other advantages:

• Improved integration between diverse clients and server applications: Multiple end-user applications running on various clients can communicate with multiple applications on a Windows^® server simultaneously. Each of the applications on the Windows server can also, simultaneously, communicate with multiple databases.

• Enhanced transaction management using Microsoft^® Transaction Server (MTS): Three-tier environments allow for more complex transactions, some of which may depend upon each other for their own successful completion. (All transactions must complete successfully in order for any of them to complete.)

• Importing iSeries data into Web pages, using Microsoft Internet Information Server (IIS): IIS can use Active Server Pages to dynamically update Web pages with data from DB2 UDB.

All three-tier environments separate components and applications into three layers. The three layers may reside on separate PCs, or terminals, and communicate over a network. Generally the tiers will have the following characteristics:

Client tier

This layer contains the interface and applications that allow end users to manipulate data. For example, this may involve a Web browser running on a network station, or a custom-built application using a remote component. This layer does not use the iSeries Access for Windows client.

Middle tier

This layer contains the business or application logic. In iSeries Access for Windows environments, this layer should consist of a Windows server running a Microsoft Active Server Pages script or a remote component.

This layer uses Microsoft's Internet Information Server (IIS) and can, optionally, use Component Services or Microsoft Transaction Server for distributed transactions. The script uses the ADO.NET provder, OLE DB provider, or ODBC driver that are included with iSeries Access for Windows. These clients communicate with the database tier to get the DB2 for i5/OS database data.

Refer to the following topics for more information about the middle-tier:

• Use Microsoft Transaction Server (MTS)

• Access iSeries services from the middle tier

Database tier

This layer usually consists of a DB2 for i5/OS database. Your applications can access this and various iSeries services through host server programs, or through custom-built iSeries programs.

• Using distributed transaction support
  The iSeries Access for Windows client supports Microsoft Transaction Server (MTS) and the Component Services model, with the iSeries Access ODBC driver and the IBMDASQL OLE DB provider.

• Access iSeries services from the middle tier
  There are several ways to provide your middle-tier components with access to iSeries services.

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