-DH Lines in a Database Block

In the -DH Lines tab, you can describe the relationships between Segments in a hierarchical database, such as DL/1.

Each line designates a Segment and its parent (except for the line that refers to the root Segment). The description consists of records and these records constitute the physical file.

This description is common to the following IMS and DL/1 hierarchical Database Block types:
  • DP: Physical database description,
  • DR: Physical database description (same as DP, but only the Data Elements that are 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. The dialog box that opens lists the available PSB databases. The code of the selected database is displayed as a link that automatically switches to the Database Block editor.
For a PSB database called on a -DH line, you must enter only 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 in the list of the available Segments. If the list is large, you can reduce it by entering a string that is used as filter (the filtering is performed on the code or on the label of the instance).
Parent Segment
Click Change to select the code of the Segment that the given Segment is hierarchically dependent on. This field is not used forIP or IS-type Database Blocks.
Relation code
This field is optional. It is used only if the type of Block is PSB to name the different DBD and PCB called.
Key indicator or Option
Enter the key indicator that is used as the symbolic reference of the key Data Element of a Segment in a Database Block. The character that is 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 the following values:
  • 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
Enter the average number of occurrences of a child Segment that is linked to one occurrence of its parent Segment.
Comment/Relationship/Key length
You can use this field to document the defined parent-child link. You can also use it 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 of the following elements:
  • A DBD called in a PSB,
  • A PCB called in a PSB,
  • An index database that is called as an independent database in the PSB.
You can override his length 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.
-G Lines
This button can be used to access the -G Lines wizard and create -GG lines that are associated with the description line. On these lines you can enter or modify information to complete the description line before the generation.

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