Local Data Areas

Currently, the fields used by your program are defined within the DEFINE DATA statement in the program itself. It is also possible, however, to place the field definitions in a local data area (LDA) outside the program, with the program's DEFINE DATA statement referencing this local data area by name. For reusability and for a clear application structure, it is usually better to define fields in data areas outside the programs.

You will now relocate the information from the DEFINE DATA statement to a local data area. When you have completed the exercises below, your sample application will consist of the following modules:

Application structure

This document contains the following exercises:

Creating a Local Data Area

You will now invoke the data area editor in which you will specify the required fields.

Start of instruction setTo create a local data area

  1. In the library workspace, select the library which also contains your program (that is: select the TUTORIAL node).

  2. From the context menu, choose New Source > Local Data Area.

    Or:
    Choose the following toolbar button:

    Local data area

    An editor window appears.

    Editor window

    Level, name, format and length are automatically preset in the first row.

Defining Data Fields

You will now define the following fields:

Level Name Format Length
1 #NAME-START A 20
1 #NAME-END A 20
1 #MARK A 1

These are the user-defined variables which you have previously defined in the DEFINE DATA statement.

You can define the data fields in two different ways: manually in the editor window where it is your responsibility to define the correct format and length of the data field, or with the Import command where you simply select the data fields from a list and where the correct format and length is automatically used. These two ways are described below.

The setting of the following toolbar button in the Data Area Editor Insert toolbar indicates the insert position. When the toolbar button appears pressed, the new field is inserted after the selected field (this state is assumed in this tutorial); otherwise, the new field is inserted before the selected field.

Toolbar button

Start of instruction setTo define a data field manually in the editor window

  1. Make sure that the Level column in the first row contains the preset value "1".

  2. Change the preset value in the Name column of the first row to "#NAME-START".

  3. Make sure that the Format column in the first row contains the preset value "A".

  4. Change the preset value in the Length column of the first row to "20".

Start of instruction setTo import data fields from a program

  1. In the editor, select the row which has been created for #NAME-START.

    Note:
    If required, press ENTER or ESC to switch from single-cell selection to full-row selection mode.

  2. From the context menu, choose Import.

    Or:
    Choose the following toolbar button:

    Import data field

    The Import Data Field dialog box appears.

  3. Make sure that TUTORIAL is selected in the Library drop-down list box.

  4. Select the Program check box.

    All programs that are currently defined in your library are now shown in the Object list box.

  5. Select the program with the name PGM01.

    The importable data fields are now shown at the bottom of the dialog box.

    Import data field

  6. Press CTRL and select the following fields in the Importable Data list box:

    #NAME-END
    #MARK

  7. Choose the Import button.

    The Cancel button in the Import Data Field dialog box is now labeled Quit.

  8. Choose the Quit button to close the Import Data Field dialog box.

    The fields #NAME-END and #MARK are now shown below the #NAME-START field in the editor window.

Importing the Required Data Fields from a DDM

You will now import the same data fields which you have previously defined in the program's DEFINE DATA statement. The fields are read directly from a Natural data view into the data area editor. A data view references database fields defined in a data definition module (DDM).

In the data area editor, the imported data fields will be inserted below the currently selected data field.

Start of instruction setTo import data fields from a DDM

  1. In the editor, select the row containing #MARK.

  2. From the context menu, choose Import.

    The Import Data Field dialog box appears.

  3. From the Library drop-down list box, select SYSEXDDM.

    The DDM option button is selected.

  4. In the Object list box, select the sample DDM with the name EMPLOYEES.

  5. Press CTRL and select the following fields in the Importable Data list box:

    PERSONNEL-ID
    FULL-NAME
    NAME
    DEPT
    LEAVE-DATA
    LEAVE-DUE

    Note:
    The field PERSONNEL-ID will be used later when you create the subprogram.

  6. Choose the Import button.

    The View Definition dialog box appears.

  7. Specify the same name that you have previously defined for your view (that is: EMPLOYEES-VIEW).

  8. Choose the OK button.

  9. Choose the Quit button to close the Import Data Field dialog box.

    The local data area should now look as follows:

    Local data area

    The Type column indicates the type of the variable. The view is indicated by a "V" and each group is indicated by a "G".

    Note:
    When the Expand/Collapse check box has been selected in the data area editor options, expand/collapse toggles are shown in the first column (for the view and each group).

  10. Stow the local data area.

  11. When you are asked to specify a name for the local data area, enter "LDA01".

    In the library workspace, a new node named Local Data Areas appears below the TUTORIAL node. This node contains the local data area you have just stowed.

Referencing the Local Data Area from Your Program

Once a local data area has been stowed, it can be referenced by a Natural program.

You will now change the DEFINE DATA statement your program so that it uses the local data area that you have just defined.

Leave the data area editor open in the background.

Start of instruction setTo use the local data area in your program

  1. Return to the program editor.

  2. In the DEFINE DATA statement, delete all variables between LOCAL and END-DEFINE.

  3. Add a reference to your local data area by modifying the LOCAL line as follows: 

    LOCAL USING LDA01

    Your program should now look as follows:

    DEFINE DATA
  LOCAL USING LDA01
END-DEFINE
*
RP1. REPEAT
*
  INPUT USING MAP 'MAP01'
*
  IF #NAME-START = '.' THEN
    ESCAPE BOTTOM (RP1.)
  END-IF
*
  IF #NAME-END = ' ' THEN
    MOVE #NAME-START TO #NAME-END
  END-IF
*
  RD1. READ EMPLOYEES-VIEW BY NAME
    STARTING FROM #NAME-START
    ENDING AT #NAME-END
*    
    IF LEAVE-DUE >= 20 THEN
      PERFORM MARK-SPECIAL-EMPLOYEES
    ELSE
      RESET #MARK
    END-IF
*
    DISPLAY NAME 3X DEPT 3X LEAVE-DUE 3X '>=20' #MARK
*
  END-READ
*
  IF *COUNTER (RD1.) = 0 THEN
    REINPUT 'No employees meet your criteria.'
  END-IF
*
END-REPEAT
*
DEFINE SUBROUTINE MARK-SPECIAL-EMPLOYEES
  MOVE '*' TO #MARK
END-SUBROUTINE
*
END

  4. Run the program.

  5. To confirm that the results are the same as before (when the DEFINE DATA statement did not reference a local data area), enter "JONES" as the starting name and press ENTER.

  6. Press ESC to close the output window.

  7. Stow the program.

You can now proceed with the next exercises: Global Data Areas.