HP Integrity NonStop J-Series - Manual (Page 103)

CREATING AND RUNNING A MULTIFILE APPLICATION
Associating and Linking Boxes
Level numbers do not have to correspond to the precise level at
which a box resides, nor do they have to be sequential. These
rules govern level numbers for the TREE attribute:
1. The numerically lowest-level number identifies the box at the
first level of the tree; only one box can have this level
number.
2. The level number of a parent box must be lower than the level
number of its child box (or boxes).
3. The level numbers for all child boxes associated with the
same parent box must be the same.
4. Valid level numbers range between 1 and 50.
Using the LINK OPTIONAL Parameter. When you supply a value for
the TREE attribute, you must use the LINK OPTIONAL parameter with
every box except the box at the first level of the tree. When
you use this parameter, you identify the link that connects a
child box to a parent box.
The LINK OPTIONAL parameter has two forms. You use the first
form if the join field of the parent box and the join field of
the child box have different names. You use the second form if
the join fields of both boxes have the same name.
If you use the first form of the LINK OPTIONAL parameter, you
enter the join-field name of the parent box before the join-field
name of the child box, for example:
SET APPL TREE (01 employee
02 dependents LINK empnum
TO OPTIONAL emp-no)
In this case:
• "employee" is the name of the parent box.
• "dependents" is the name of the child box.
• "empnum" is the join field of the parent record.
• "emp-no" is the join field of the child record.
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