Rational Programming Patterns

Managing errors in Servers

The Business Component implements the services associated with a Logical View. As it runs the service, it can detect errors. In this case, it must send all the error information in its reply message to the client so that the client can take the appropriate action.

Principle

The following two types of errors are possible:
  • Standard errors detected after the standard accesses to Segments or the validation of the Logical View data. You can modify the messages associated with these errors.
  • Specific errors, which correspond to errors you describe entirely in source code.
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When a Business Component detects an error, it immediately performs a ROLLBACK operation before sending back the reply containing the errors. It gives the control back to the client without calling the next Business Component

Implementation

  1. Enter the following options on O-type lines, in the -GO Lines of the following entities:
    • ACCESERR and DATAERR in the Business Component. These two options define the number of errors that the Business Component can detect before giving the control back to the calling program. For a TUI application, both these options are required.
    • ACCESERR, DATAERR, ERRLAB and ERRSERV in the Server Dialog for single-view development.
  2. Describe in each Business Component and Logical View the error messages associated with the codes of the errors specified with specific code, These errors correspond to the errors set in the Business Component with the ERU (user error), ERR (error on Data Element) or ERL (logical lock or unlock error) operators. You indicate the messages associated with these errors on U-type lines in the -GE Lines of the following entities:
    • Business Component for the errors specified with ERU or ERL,
    • Logical View for the errors on specified with ERR.
    Note: You can also modify the messages associated with standard errors. These errors are detected after standard accesses to Segments or checks on Logical View data.
  3. Create and describe the error message server in order to access the error message file.
    To process the errors, the following four variables are generated in the WORKING-STORAGE SECTION of the Business Component:
    • IER: Number of errors on Segment access, initialized by the ACCESERR option
    • IED: Number of errors on Data Element, initialized by the DATAERR option
    • K50L: Work index of the number of errors on Segment access
    • K50D: Work index of the number of errors on Data Element
  4. Generate the error message file. The generated file is a sequential file from which you create the error message file for your application, with the appropriate organization (relational table, VSAM file for example). An error message file includes 100-character records whose structure contains the following elements:
    • An access key (ERKEY, 29 characters)
    • A code for the severity of the error (one character: E for error, W for warning)
    • The message itself

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