Error Handling Overview

Error Handling Overview

Figure 1 shows the complete error-handling structure for both OPM and ILE programs. This figure is used throughout this manual to describe advanced error-handling capabilities. This topic gives a brief overview of the standard language error-handling capabilities. For additional information on error handling, refer to Error Handling.

The figure shows a fundamental layer called exception-message architecture. An exception message may be generated by the system whenever an OPM program or an ILE program encounters an error. Exception messages are also used to communicate status information that may not be considered a program error. For example, a condition that a database record is not found is communicated by sending a status exception message.

Each high-level language defines language-specific error-handling capabilities. Although these capabilities vary by language, in general it is possible for each HLL user to declare the intent to handle specific error situations. The declaration of this intent includes identification of an error-handling routine. When an exception occurs, the system locates the error-handling routine and passes control to user-written instructions. You can take various actions, including ending the program or recovering from the error and continuing.

Figure 1 shows that ILE uses the same exception-message architecture that is used by OPM programs. Exception messages generated by the system initiate language-specific error handling within an ILE program just as they do within an OPM program. The lowest layer in the figure includes the capability for you to send and receive exception messages. This can be done with message handler APIs or commands. Exception messages can be sent and received between ILE and OPM programs.

Figure 1. Error Handling for OPM and ILE

Language-specific error handling works similarly for ILE programs as for OPM programs, but there are basic differences:

• When the system sends an exception message to an ILE program, the procedure and module name are used to qualify the exception message. If you send an exception message, these same qualifications can be specified. When an exception message appears in the job log for an ILE program, the system normally supplies the program name, module name, and procedure name.
• Extensive optimization for ILE programs can result in multiple HLL statement numbers associated with the same generated instructions. As the result of optimization, exception messages that appear in the job log may contain multiple HLL statement numbers.

Additional error-handling capabilities are described in Error Handling.