Host Transaction Integration

Many organizations use host computer systems to support real-time transaction processing applications, such as IBM's CICS. These applications are accessed through interactive sessions with the host system, such as a 3270 or 5250 session supported by a terminal emulator.

We have already described how the SNA Server's COMTI feature can be used to access simple mainframe applications at the program level. This feature becomes an even more powerful tool when used to extend applications that use Windows 2000 Server Component Services. Windows-based applications that use Component Services can coordinate transactions with mainframe-based CICS applications.

When coupled with Component Services, COMTI can be used for a variety of purposes:

• Windows developers can describe, execute, and administer special Component Services objects that access CICS or IMS transaction programs (TPs).
• Mainframe developers can make mainframe TPs available to Windows-based Internet and intranet applications.
• Component Services component designers can include mainframe applications within the scope of Component Services two-phase commit transactions.

Developers using Component Services in their applications can decide which parts of the application require a transaction and which parts do not. COMTI extends this choice to the mainframe, as well, by handling both calls that require transactions and calls that do not.

For applications that require full integration between Windows-based two-phase commit and mainframe-based Sync Level 2 transactions, COMTI provides all the necessary functionality without requiring you to change the client application. Also, no executable code needs to be placed on the mainframe, and little or no changes to the mainframe TPs are required. The client application does not need to distinguish between the COMTI component and any other Component Services component reference.

Figure 10.31 illustrates how a Windows-based client application implicitly uses the Distributed Transaction Coordinator (DTC) to coordinate a distributed transaction involving SQL Server and a CICS transaction program. The DTC is the part of Component Services that coordinates two-phase commit transactions.

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Figure 10.31 Integration with Host Transaction System

Complete information about using COMTI, including sample applications, can be found in the SNA Server version 4.0 documentation.

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