Referential integrity checks
Goal - prevent addition of new inconsistencies
When deleting person, role or maintainer object check is made if there are objects in the database which refer to object being deleted in their admin-c, tech-c, zone-c, cross-nfy, mnt-by, mnt-lower or cross-mnt attributes. If yes delete operation is refused.
During object creation or modification check is made whether objects referenced in admin-c, tech-c, zone-c, cx-nfy, mnt-by, mnt-lower and cx-mnt attributes do exist in the database. Operation is refused when references to non-existing objects found.