Abstract: A system for recovery of relations in a data base in case of errors, comprises functionality executed by a computer and ensuring that data in the data base are structured as items of data in a number of recovery sub-systems, each item of data belonging to only one sub-system. If a sub-system contains one or more items of data that depend on one or more items of data in another sub-system, the first mentioned sub-system is marked as depending on the second mentioned sub-system. If a first sub-system is marked as depending on a second sub-system which is marked as depending on a third sub-system, the first sub-system is recursively marked as depending on the third sub-system. Furthermore no two sub-systems are marked as depending on each other. Integrity constraints between an item of data in one sub-system and an item of data in another sub-system are admitted provided that one of these sub-systems is marked as depending on the other one.