Avoiding abnormal termination

You must avoid creating a physically deleted logical child that can be accessed from below in the physical structure (using its third path). A logical child can be accessed from below if any of its physical dependents are accessible through logical paths.

• Method 1
  The first method requires that logical paths to dependents be broken before the logical child is physically deleted. Breaking the logical path with method 1 is done using a P rule for the dependents as long as no physical deletes are propagated into the database. Therefore, no V rules on logical children can be allowed at or above the logical child, because, with the V rule, a propagated logical delete causes a physical delete without a P rule violation check. The L rule also causes propagation, if the PD bit is already set on, but the dependent's P rule will prevent that case. Similarly, no V rule can be allowed on any logical parent above the logical child, because the logical delete condition would cause the physical delete.
• Method 2
  The second method requires breaking the logical path whenever the logical child is physically deleted. Breaking the logical path with this method is done for subordinate logical child segments using the V delete rule. Subordinate logical parent segments need to have bidirectional logical children with the V rule (must be able to reach the logical children) or physically paired logical children with the V rule. This method will not work with subordinate logical parents pointed to by unidirectional logical children.