Rational Programming Patterns for System z

-DH lines in a Database Block

In the -DH lines tab, you can describe the relationships between Segments in a hierarchical database (example: DL/1).

Each line designates a Segment and its parent (except for the line referring to the root Segment). The description consists of records which make up the physical file.

This description is common to the following IMS / DL/1 - hierarchical Database Block types:
  • 'DP': Physical database description,
  • 'DR': Physical database description (same as 'DP', but only the Data Elements referenced as access keys in the Segment description are generated in the FIELD statements),
  • 'DL': Logical database description,
  • 'PC': PCB,
  • 'IP': Primary index,
  • 'IS': Secondary index.

-DH lines definition

The -DH lines definition section is displayed when you enter or click a description line. In this section, you can enter information about the description line.

Definition
The Block code field is active only for PS-type Blocks. To select PSB Database Block, you must click Change. In the dialog box which opens up, you find a list where you can select instances among the available PSB databases. The code of the selected database is displayed as a link that switches you to the Database Block editor.
For a PSB database called on a -DH line, you only must enter the Key indicator or option and Comment/relationship/key length fields.

The following Segment options are active for all Block types other than the PC or PS type.

Segments
Select the Segment code. SOCRATE/CLIO database: Select the code of the Segment which is used to generate the entity, the formal or the SOCRATE/CLIO Segment. To enter or modify the contents of this field, click Change. In the dialog box that opens, you can select a Segment code in the list of the available Segments or create a Segment.
Parent Segment
Click Change to select the code of the Segment upon which the given Segment is hierarchically dependent. This field is not used for IP or IS-type Database Blocks.
Relation code
This field is optional. It is only used if the type of Block is 'PSB' to name the different DBD and PCB called.
Key indicator or Option
Enter the key indicator used for a symbolic reference of the key Data Element of a given Segment in a given Database Block. The character indicated in this field must also be entered in the -CE lines of the Segment, in the Sort key field of the Data Element call line.
In this field, you can enter:
  • U to indicate a unique key,
  • M to indicate a multiple key
  • a digit between 1 and 9 to indicate a DL/1 Secondary index,
  • $ in a PCB or a physical or logical DBD, if you want to generate a non-qualified SSA,
  • any other values to indicate a search field.
Note: Key indicators are not permitted on Data Elements that are used to redefine other Data Elements.
Estimated number of links
You enter here the average number of occurrences of a child Segment linked to one occurrence of its parent Segment.
Comment/Relationship/Key length
This field can be used to document the defined parent-child link. It is also used to indicate the concatenated key length.
When generating PS-type Database Blocks (a PSB), the length of the longest concatenated key is automatically calculated for each:
  • DBD called in a PSB,
  • PCB called in a PSB,
  • Index database called as an independent database in the PSB.
This length can be overridden by entering the following characters on the first line: CC=n (with n = 9 - 9999).
On each Segment call line, you can enter PR=nnnn to generate the PROCOPT=nnnn parameter in the SENSEG statement when generating the PSB which contains this DBD, PCB, or index database.
Note: The length is calculated only for a primary Segment. In the case of a secondary index, the CC= parameter is required.

-GG Lines

The -GG lines section is displayed when you enter or click a description line. In this section, you can enter information to complete the description line.

In the -GG lines, you can modify the information contained in the Block Description lines before they are generated. Depending on the type of description line, lines are automatically displayed, in order to guide you when you enter the physical information of the Block. These lines are identified by 'VIRT' or 'GUID' in the last field of the table of the -GG lines. Collectively, these lines are called 'virtual' lines. The lines identified by 'VIRT' are generated. To modify these lines, you must override them and create new lines between beginning and end insertion lines. When you select a virtual line and click Override, the 'VIRT' or 'GUID' line is changed into a 'FromVIRT' or 'FromGUID' line. Then it can be modified. You can also edit the FromGUID and FromVIRT lines by selecting them and pressing the F2 key. You can create lines anywhere in the table. However if you want them to be taken into account at generation time, you must identify them with a G Type.

In the table, you find the following data-entry fields:
Type
When you click this field, you can select a line type among:
  • *: comment lines to be generated,
  • V: lines generated before the automatically generated elements,
  • G: line generated instead of the automatically generated elements,
  • P: lines generated between the element automatically generated parts and its description,
  • Z: lines generated after the automatically generated elements,
    Note: P and Z types are available only for -GG lines associated with CODASYL Block definition and -DC lines.
Description
This field must be used to enter the generation elements or comments to be generated. Its content depends on the type of Block and type of line selected.

Terms of use | Feedback

This information center is powered by Eclipse technology. (http://www.eclipse.org)