Planning and Designing XARs

For a great majority of the applications that use XARs, the process of implementing an XAR is simple and straightforward. However, for some more complicated applications, you need to plan ahead and design the required XAR(s) to accommodate the complexity of such an application.

Once you have generated an RM switch module, 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, providing the best possible configuration for running applications on Enterprise Server.

XARs support the following RM switch module types:

• SQL Server
• IBM DB2
• Oracle
• Generic one-phase commit for ODBC

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 region without having to recompile your source code with the XAID compiler directive.

However, in some scenarios, more than one XAR of the same type might be required for a Web services application. In this case, you must compile your code using the XAID compiler directive, in addition to providing multiple XAR definitions. See Working with Multiple XARs for more information.

Is the application coded to use distinct XARs?

Typically, the SQL code of Web Services requests are 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 configure an XAR for an enterprise server region.