Planning and Designing XARs

For a great majority of the applications that use XARs, the process of implementing an XAR is simple and straightforward, requiring only that you define the XAR in Enterprise Server. For more information about defining an XAR, see To define an XAR for an enterprise server region.

However, for a more complicated application, you need to plan ahead and design the required XAR(s) to accommodate the complexity of such an application. This can require modification and recompilation of application source code, and compilation of XAR switch module source code, which is provided with our Visual COBOL product. For more information on this process, see the Planning and Designing XARs topic in your Visual COBOL documentation.

After building a Micro Focus RM switch module in Visual COBOL, you can include it in an XAR definition in Enterprise Server. An XAR definition includes an xa_open string, which is where you include specific RM syntax for the underlying RM.

In addition to the RM-specific xa_open string syntax, we provide several options that enable you to fine-tune your XAR definitions to yield maximum efficiency when running applications on Enterprise Server.

XARs support the following RM switch module types:

• IBM DB2
• Oracle
• Generic one-phase commit for ODBC
• EDB PostgreSQL (early adopter program)

Before configuring an XAR for an enterprise server region, we suggest that you consider the following:

Does the application require more than one XAR?

This depends on what database(es) the application accesses, and how the application interacts with it.

Do any applications require more than one XAR of the same RM switch module type?

If your application does not require more than one XAR of the same RM switch module type, then you are ready to define your XAR(s) in your enterprise server instance .

However, in some scenarios, more than one XAR of the same type might be required for a Web services application. This likely requires recompilation of application source code. See Working with Multiple XARs for more information.

Is the application coded to use distinct XARs?

Typically, the SQL code of Web service requests is stored in distinct source code modules – some modules used with only one database, and others used with another. Code constructed in this fashion can be compiled for each program module using the XAID compiler directive option set to the value of the appropriate XAR ID. This eliminates the need to change code.

Is it best to use a static or dynamic RM switch module in an XAR?

This depends on how the XAR is accessed by the application(s). See RM Switch Module Registration for more information.

For more information about configuring an XAR, see To define an XA Resource (XAR) for an enterprise server instance.