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Semantics-based locking

from isolation to cooperation

'Advanced database applications', such as CAD/CAM, CASE, large AI applications or imageand voice processing, place demands on transaction management which differ substantially from those of traditional database applications. In particular, there is a need to support 'enriched' data models (which include, for example, complex objects or version and configuration management), 'synergistic' cooperative work, and application- or user-supported consistency. This paper deals with a subset of these problems. It develops a methodology for implementing semantics-based concurrency control on the basis of ordinary locking. More specifically, it will be shown how conventional locking can step by step be improved and refined to finally reach our initial goal, namely a comprehensive support of synergistic cooperative work by the exploitation of application-specific semantics. In addition to the 'conventional' binding of locks to transactions we consider the binding of locks to objects (object related) and subjects (subject related locks). Object related locks can define persistent and adaptable access restrictions on objects. This permits, among others, the modeling of different types of version models (time versions, version graphs) as well as library (standard) objects. Subject related locks are bound to subjects (user, application, etc.) and can be used among others to supervise or direct the transfer of objects between transactions.

Titel: Semantics-based locking
Untertitel: from isolation to cooperation
Verfasser: Unland, Rainer GND
Organisation: FB 04: Wirtschaftswissenschaftliche Fakultät
Dokumenttyp: Arbeitspapier
Medientyp: Text
Erscheinungsdatum: März 1994
Publikation in MIAMI: 21.09.2008
Datum der letzten Änderung: 27.01.2015
Reihe Arbeitsberichte des Instituts für Wirtschaftsinformatik ; 31
Fachgebiete: Wirtschaft; Datenverarbeitung; Informatik
Sprache: Englisch
Format: PDF-Dokument
URN: urn:nbn:de:hbz:6-43599554344
1 Introduction ..... 4
2 Lock modes ..... 11
2.1 Extended set of lock modes ..... 12
2.2 The two effects of a lock ..... 13
2.3 The Semantics of the Lock Modes ..... 16
2.4 A short discussion of consistency aspects ..... 17
2.5 Dynamic Assignment of an External Effect (Open Lock) ..... 17
2.6 Upgrading a lock ..... 18
3 Locks in the Context of Nested Transactions ..... 20
4 Rules on Locks and Notification Services ..... 22
5 Object-related Locks ..... 26
6 Subject-related Locks ..... 29
7 Conclusion ..... 32
Literature ..... 32