Abstract: For backing up in a distributed real time data base on primary memory in operation, all data in the data base are structured as belonging to one of several logic data bases. The logic data can, but need not, extend over several processors. A backup function of a certain logic data base is activated by sending a message to a central backup handler, which has information regarding processors, over which the current backup system extends, and synchronizes the backup function over processor borders. The synchronization includes that local data base handlers are informed that backup will be started and that a new transaction log is being created, in which all transactions that have not attained a commit state and which shall therefore not be included in the backup are logged. The backup will only contain changes of transactions in the old transaction log.

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.