Specifying rules in the physical DBD

Insert, delete, and replace rules are specified using the RULES= keyword of a SEGM statement in the DBD for logical relationships.

The following figure contains a diagram of the RULES= keyword and its parameters.

Figure 1. Insert, delete, and replace rules in the DBD
Read syntax diagramSkip visual syntax diagramSEGMOther parameters,RULES=(LLL,LAST),RULES=(LLLLPVLPVBLPV,LAST,FIRST,HERE)
The valid parameter values for the insert replace and delete rules are:
B
Specifies a bidirectional virtual delete rule. It is not a valid value for either the first or last positional parameter of the RULES= keyword.
L
Specifies a logical insert, delete, or replace rule.
P
Specifies a physical insert, delete, or replace rule.
V
Specifies a virtual insert, delete, or replace rule.
The first three values that the RULES= keyword accepts are positional parameters:
  • The first positional parameter sets the insert rule
  • The second positional parameter sets the delete rule
  • The third positional parameter sets the replace rule

For example, RULES=(PLV) says the insert rule is physical, the delete rule is logical, and the replace rule is virtual. The B rule is only applicable for delete. In general, the P rule is the most restrictive, the V rule is least restrictive, and the L rule is somewhere in between.

The RULES= parameter is applicable only to segments involved in logical paths, that is, the logical child, logical parent, and physical parent segments. The RULES= parameter is not coded for the virtual logical child.