Abstract: A method is provided for consistent reading of a number of objects (1O, 2O, 3O) within a database. The method is adapted for use with a database in which transactions are managed by two-phase locking. A first phase (A) includes a request for access to objects (1O, 2O, 3O) affected by the transaction and locking of these objects as soon as access thereto has been granted. A second phase (B) includes committing the transaction and releasing all locks that were set in the first phase. The actual work performed in a transaction may be summarized as object changing actions and/or object non-changing actions. A change, or an update, of the content of an object is performed by writing the new content into a new version of the object, where the current version of the object prior to the transaction is retained until no further transactions make use of this version. The transaction performs all changing actions within the first phase (A).

Abstract: In a distributed data base system, different parts of the data base are handled by each of a number of interconnected processors. The different data base parts contain a number of data entities. There are provided for each of such data entities global information relating to the processor in which the data entity is located, and local information relating to the location of the data entity in the own processor. The global information is located in each processor in the system in the form of global information common to and specific for each set of data entities. More particularly, the sets of data entities comprise distribution entities each of which includes information relating to a number of instances of a certain type of data entity located in a certain processor, and information by which the address to this processor can be found.

Abstract: In a distributed data base system, different parts of the data base are handled by each of a number of interconnected processors. The different data base parts contain a number of data entities. There are provided for each of such data entities global information relating to the processor in which the data entity is located, and local information relating to the location of the data entity in the own processor. The global information is located in each processor in the system in the form of global information common to and specific for each set of data entities. More particularly, the sets of data entities comprise distribution entities each of which includes information relating to a number of instances of a certain type of data entity located in a certain processor, and information by which the address to this processor can be found.