Expect to come across this popular question in Mainframe Interview Questions. To limit the number of potential modifications that may be made to a main key by using a foreign key, self-referencing limitations are used. To make this possible, the foreign keys need to specify a rule known as the DELETE-CASCADE rule. This rule stipulates that if the relationship for the DELETE rule is specified as CASCADE, then additional rows in the table will be recursively destroyed if one row is updated or deleted.