The EXCI User Exit

The EXCI client supports an optional user exit named DFHXCURM, as defined by the IBM EXCI documentation. You can write a module that implements this exit and configure the EXCI client layer to load and call it. (The exit program can be written in any .NET language, but because the interface is defined as a COBOL group item, additional work is required to implement it in any language other than COBOL.)

The EXCI user exit receives certain parameters regarding each client request, and has the option of changing the APPLID that identifies the target region before the request is made. This has two main uses:

1. The exit can be used to change the APPLID in order to change the request destination without changing the client application source code. This may be useful to temporarily redirect a client, or to switch between test and production regions, for example.
2. The exit can change the APPLID when an EXCI request fails because the target region is not available. This can be used as a form of failover processing.

A sample DFHXCURM user exit is included with Enterprise Server for .NET.