Rational Programming Patterns for System z

Call of Data Element groups in a Logical View

To display the content of the Group definition section, you must select a Data Element group within the Logical View call lines. A group is a set of elementary Data Elements. In the Group definition section, you indicate the name and label of the group, and the number of occurs. You must click More to indicate the definition of the group. From this section, you can also define or modify the -G lines of the group of Data Elements.

You can insert Data Element groups in the -CE lines composition of a Logical View, these are elementary Data Elements. A group can include other groups. All the elementary Data Elements are then counted to define the group. There can be nine nested levels maximum. It is strictly forbidden to use the same Data Element more than once in the Logical View composition.

Name
Enter the code of the group. The code you enter here is free, but cannot exceed six characters. You can change the group code or label at any moment, after the group is created.
Label
Enter a label of the group you have created. The label you enter here is free but cannot exceed 36 characters. You can change the group label at any moment, after the group is created.
Occurs
In this field, you enter the number of occurrences on three numeric characters. It corresponds to the OCCURS clause. It is not possible to have a repeated group area apart from the repeated structure (see the Data Type field). Repeated Data Elements are not authorized in graphic applications.

Logical View attributes

Data type
When a client calls a selection service, this service can implement an extraction method and its parameters by value. The Business Component which answers the call must recognize the extraction method and its parameters to correctly perform the service. The only way to send this information is through the message sent by the client.

The extraction method is sent to the Business Component through the technical part of the message. Parameters must be described in the application part of the message, that is in the Logical View.

In the Data type field, you specify the parameters by value for all the extraction methods which can be used by the Logical View. To do so, you call Data Elements defined in the Pacbase repository. For each parameter, you enter the E type, which indicates that it is a parameter. Each identifier Data Element (U type) is an implicit parameter. The other Data Elements that describe the contents of the Logical View cannot be used as parameters. The E-type Data Element does not belong to the description of a Logical View. If necessary, you can define and call a child Data Element.
Table 1. Specification of the data type
Options Description
None Data Element not used as a parameter. For Data Elements describing the Logical View.
U: identifier for paging Data Elements which are to be used as selection criteria or start key for the reading of data occurrences in the database. Identifier for the paging of a list for the client. As output from the server, it contains the selection criteria values of the next page.
R: repeated structure There is only one repeated structure for one Logical View. A repeated structure is specified in the group Data Elements. This Data Element indicates the beginning of the repeated Data Elements. The end of the repeated Data Elements is deduced from the number of Data Elements in a group. The number of occurrences must be indicated in the Number of occurrences field in the Logical View definition.
E: extraction parameter The Data Element is used as a parameter for an extraction method. The 'E' type Data Elements must be entered in the '-CE' lines before the Data Elements that describe the Logical View contents. Each identifier Data Element ('U' type) is an implicit extraction parameter. The other Data Elements describing the Logical View cannot be used as parameters. If necessary, you can define and call a child Data Element.
Data Element presence
For each called Data Element, select one of the following check options in the list:
Table 2. Specification of the Data Element presence
Options Description
O: required Required Data Element. The check for its presence is generated in the client, and in the Business Component if CHECKSER=YES.
Note: includes checks in relation to the Data Element description.
P: required Required Data Element. The check for its presence is generated only in the Business Component, if CHECKSER=YES.
Note: includes checks in relation to the Data Element description.
Blank The checks specified in the Data Element description are generated in the client, and in the Business Component, if CHECKSER=YES.
F: optional The checks specified in the Data Element description are only generated in the Business Components if CHECKSER=YES.
Direction of transfer
For each Data Element called in a Logical View, you must select the data transfer direction between the client and the server:
Table 3. Possible values for the transfer direction
Options Comments
Both directions Default value for an update service or a selection service. It is the required value for graphic applications.
C: Client to Server Client to Business Component: From Logical View to Segment for an update service.
S: Server to Client Business Component to client: From Segment to Logical View for a selection service.

The direction of the transfer must also be indicated in the group Data Elements. The repeated Data Elements must have the same transfer direction. This direction can be indicated on the Data Elements bordering the repeated data (Data Element with an R indicator). You enter the C or S value in this Data Element only if the Direction of transfer field in the Logical View Definition tab is 'both directions'.

Redefines
Redefinition is possible within a Segment or Logical View. It generates the COBOL REDEFINES clause. The Data Element containing this option redefines the Data Element of the same COBOL level which precedes it in the -CE lines. If a Data Element which redefines another Data Element is contained in a group, it is considered to be an elementary Data Element. It must be taken into account in the calculation of the number of Data Elements contained in a group (except for DL/1 database Segments).
Note: When Data Elements are redefined, their respective lengths are not taken into account. It is your responsibility. The redefined Data Element length is used for the address calculation. Redefined Data Elements are ignored when generating for the Database Description function. If the Redefines box is checked, no initial value can be entered.
To redefine a Data Element, check the Redefines option. A Set of Redefines line is created in the -CE lines. It contains the redefined Data Element and the preceding one of the same level in the tree structure. You must then define the Occurs option in the Set of Redefines section.

More

Click More... to open a definition wizard. In this wizard, you indicate to which subschemas the Data Element group called in the Logical View must belong.

-G Lines

Click -G Lines... to define -GC lines (comments), -GE lines (error messages), and -GG lines (generation elements) for each Data Element group called in the Logical View.


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