The tab dedicated to the description lines is specific
to the type of Database Block that has been defined in the Database
Block editor. You find the -DH Lines tab, which
is specific to the hierarchical Database Blocks, the -DR
Lines tab specific to the relational Database Blocks and
the -DC Lines tab dedicated to the CODASYL, DMSII
and TANDEM Database Blocks.
About this task
What are the description lines used for?
- The -DH lines are used to describe the relationships between Segments
in a hierarchical database (example: DL/1).
- In the -DR lines, you specify which SQL objects make up the relational
database (table spaces, tables, table views, index, or key).
- The -DC lines are used to logically describe a CODASYL schema
or subschema, that is: declare areas, call records and distribute
them among areas, define, and describe sets (code, name, owner record,
member record).
The procedure to create description lines is the same for all
Database Block types. In the tab dedicated to the description lines
of a Block, you can specify the description lines of the current Block
in a tree structure list. You can also delete some of them, reorganize
them in the list. The other part of the window displays definition
sections that open when you select a description line in the list.
In these sections, you can give further information about the selected
description line. Moreover, in the
-GG lines section, you can specify generation elements associated with the
selected description line too.
Procedure
- To create a -DC line, click the Add -DC line button. As a result, a default
line is created in the list. You can change
the line type in the -DC lines definition section
displayed in the second part of the tab and you can create -GG lines
associated with the -DC line by using templates in the -GG lines section.
- To create a -DH line, click the Add -DH line button. As a result, a default
is created in the list. In the -DH lines definition section, when you select a Segment,
parent Segment or child Segment for the generation of the description
line, the Segments name is displayed in the list and identifies the
description line. You can create generation elements for the -DH line
in the -GG lines section.
- In the -DR line tab, you can create
-DR lines that display the objects type, external names, the code
of the Segments which represent them, and K-type lines which represent
the key type supported by the Segment and the generation code.
- To create a -DR line, click the Add –DR line button. A default
line is created. You can change the type
of SQL record in the -DR lines definition section
displayed in the second part of the tab. The external name followed
by the table or view code specified in this section are instantly
displayed in the list to identify the description line. You can then
add -GG lines to modify the -DR line in the -GG lines section.
- In the -GG lines section, you
find a table with 'templates' that help you specify generation
elements for the selected -DR line.
- You can create -K lines (K for
keys) under a line that describes an SQL record and whose type is
index, alter table or primary key. To do so, click the description
line under which the -K line is to be created, then click the Add -DR –-K line button. As a result, a default
line is created in the list. In the -K line definition section displayed at the bottom of the tab, you can specify the
composition of the Segment which represents the SQL record (index,
alter table or table key). The Data Element and order type you have
selected for the key are then displayed in the list to identify the
description line.