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Step 3: Adding Error Flow Redirection

As demonstrated in the previous task, the Lookup Currency Key transformation cannot generate a match when the transformation tries to process the corrupted sample flat file, which produced an error. Because the transformation uses the default settings for error output, any error causes the transformation to fail. When the transformation fails, the rest of the package also fails.

Instead of permitting the transformation to fail, you can configure the component to redirect the failed row to another processing path by using the error output. Use of a separate error processing path lets you do a number of things. For instance, you might try to clean the data and then reprocess the failed row. Or, you might save the failed row along with additional error information for later verification and reprocessing.

In this task, you will configure the Lookup Currency Key transformation to redirect any rows that fail to the error output. In the error branch of the data flow, these rows will be written to a file.

By default the two extra columns in an Integration Services error output, ErrorCode and ErrorColumn, contain only numeric codes that represent an error number, and the ID of the column in which the error occurred. These numeric values may be of limited use without the corresponding error description.

To enhance the usefulness of the error output, before the package writes the failed rows to the file, you will use a Script component to access the Integration Services API and get a description of the error.

To configure an error output

  1. In the Toolbox, expand Data Flow Transformations, and then drag Script Component onto the design surfaceof the Data Flow tab. Place Script to the right of the Lookup Currency Key transformation.

  2. In the Select Script Component Type dialog box, click Transformation, and click OK.

  3. Click the Lookup Currency Key transformation and then drag the red arrow onto the newly added Script transformation to connect the two components.

    The red arrow represents the error output of the Lookup Currency Key transformation. By using the red arrow to connect the transformation to the Script component, you can redirect any processing errors to the Script component, which then processes the errors and sends them to the destination.

  4. In the Configure Error Output dialog box, in the Error column, select Redirect row, and then click OK.

  5. On the Data Flow design surface, click Script Component in the newly added Script Component, and change the name to Get Error Description.

  6. Double-click the Get Error Description transformation.

  7. In the Script Transformation Editor dialog box, on the Input Columns page, select the ErrorCode column.

  8. On the Inputs and Outputs page, expand Output 0, click Output Columns, and then click Add Column.

  9. In the Name property, type ErrorDescription and set the DataType property to string [DT_WSTR].

  10. On the Script page, verify that the LocaleID property is set to English (United States.

  11. Click Edit Script to open Microsoft Visual Studio Tools for Applications (VSTA). In the Input0_ProcessInputRow method, type or paste the following code.

    [Visual Basic]

      Row.ErrorDescription = 
        Me.ComponentMetaData.GetErrorDescription(Row.ErrorCode)
    

    [Visual C#]

    Row.ErrorDescription = this.ComponentMetaData.GetErrorDescription(Row.ErrorCode);
    

    The completed subroutine will look like the following code.

    [Visual Basic]

    Public Overrides Sub Input0_ProcessInputRow(ByVal Row As Input0Buffer)
    
      Row.ErrorDescription = 
        Me.ComponentMetaData.GetErrorDescription(Row.ErrorCode)
    
    End Sub
    

    [Visual C#]

    public override void Input0_ProcessInputRow(Input0Buffer Row)
        {
    
            Row.ErrorDescription = this.ComponentMetaData.GetErrorDescription(Row.ErrorCode);
    
        }
    

  12. Build the script to save your changes, and then close VSTA.

  13. Click OK to close the Script Transformation Editor dialog box.

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