We continously performed research on different aspects of Parallel database systems (PDBS) between 1985 and 2001. Early work focussed on concurrency and coherency control in Shared-Disk DBMS and closely coupled SD systems.

We then investigated various kinds of dynamic load balancing for multi-user query workloads. For dynamic load balancing we also considered Shared Nothing and a dynamic redistribution of data, particularly for parallel join processing. Here we developed new algorithms for dynamically determining the number of join queries and for their processor allocation (VLDB93, VLDB95). These decisions are made dependent on the current utilization of multiple resources, in particular, CPU and memory/disk. Performance evaluations were mostly done by simulations (partly trace-driven).

Lastly, within a DFG project (1997-2001) we also considered data allocation especially for SD-based data warehouses. A new data allocation tool, Warlock (Warehouse allocation to disk) was developed and demoed at VLDB 2001 in Rome, Italy (poster, demo).

Selected Publications:

Märtens, H. Beiträge zur dynamischen Lastbalancierung in parallelen Datenbanksystemen Dissertation, Univ. Leipzig 2008

Märtens, H.; Rahm, E.; Stöhr, T. Dynamic Query Scheduling in Parallel Data Warehouses. Concurrency and Computation: Practice and Experience. Volume 15, Issue 11-12, Sep. 2003, Pages 1169 - 1190 2003

Märtens, H.; Rahm, E.; Stöhr, T. Dynamic Query Scheduling in Parallel Data Warehouses. Proc. EURO-PAR 2002, Springer-Verlag, LNCS, Paderborn, Aug. 2002 2002

Spruth, W., Rahm, E. Sysplex-Cluster-Technologien für Hochleistungs-Datenbanken. Datenbank-Spektrum Vol. 2, Heft 3, 16-26 (Mai 2002) 2002

Märtens, H. A Classification of Skew Effects in Parallel Database Systems. Proc. 7th Intl. Euro-Par Conference (Euro-Par 2001), LNCS, Springer-Verlag, Manchester, August 2001. 2001

Stöhr, T. Analytische Bestimmung einer Datenallokation für Parallele Data Warehouses. Proceedings of BTW01 (Datenbanksysteme für Büro, Technik und Wissenschaft), Oldenburg, March 2001. Springer-Verlag 2001

Stöhr, T.; Rahm, E. Warlock: A Data Allocation Tool for Parallel Warehouses. Proc. 27th Intl. Conference on Very Large Databases (VLDB), Rome, Italy, Sep. 2001 (software demonstration) 2001

Stöhr, T.; Märtens, H.; Rahm, E. Multi-Dimensional Database Allocation for Parallel Data Warehouses Proc. 26th Intl. Conference on Very Large Databases (VLDB), Cairo, Egypt, Sep. 2000 2000

Märtens, H. On Disk Allocation of Intermediate Query Results in Parallel Database Systems Proceedings Euro-Par Conf., Toulouse, LNCS, Springer 1999 1999

Rahm, E.; Märtens, H.; Stöhr, T. On Flexible Allocation of Index and Temporary Data in Parallel Database Systems. Proc. 8th Int. Workshop on High Performance Transaction Systems, Asilomar, Sep. 1999 1999

Märtens, H. Skew-Insensitive Join Processing in Shared-Disk Database Systems Proc. Issues and Applications of Database Technology (IADT’98), Berlin, 1998 1998

Rahm, E. Dynamic Load Balancing in Parallel Database Systems Proc. EURO-PAR 96 Conf, LNCS 1123, Springer-Verlag, Lyon, Aug. 1996 (Keynote Paper) 1996

Rahm, E.; Marek, R. Dynamic Multi-Resource Load Balancing in Parallel Database Systems Proc. 21th Int. Conf. on Very Large Database Systems, Zurich, Sep. 1995 1995

Rahm, E.; Stöhr, T. Analysis of Parallel Scan Processing in Shared Disk Database Systems Proc. EURO-PAR, Stockholm, Springer-Verlag, LNCS, Aug. 1995 1995

Rahm, E. Mehrrechner-Datenbanksysteme 1994

Rahm, E.; Marek, R. Analysis of Dynamic Load Balancing Strategies for Parallel Shared Nothing Database Systems Proc. 19th Int. Conf. on Very Large Database Systems, Dublin, August 1993, pp. 182-193 1993

Marek, R.; Rahm, E. On the Performance of Parallel Join Processing in Shared Nothing Database Systems Proc. 5th Int. PARLE Conf. (Parallel Architectures and Languages Europe), Springer Lecture Notes in Computer Science 694, pp. 622-633 1993

Rahm, E. Concurrency and Coherency Control in Database Sharing Systems. Technical Report, Dec. 1991, revised: March 1993 1993

Rahm, E. Empirical Performance Evaluation of Concurrency and Coherency Control Protocols for Database Sharing Systems ACM Transactions on Database Systems, Vol. 18, No. 2, June 1993, pp. 333-377. 1993

Rahm, E. Evaluation of Closely Coupled Systems for High Performance Database Processing Proc. 13th Int. Conf. on Distributed Computing Systems, Pittsburgh, USA, May 1993, IEEE Computer Society Press, pp. 301-310 1993

Rahm, E. Hochleistungs-Transaktionssysteme 1993

Rahm, E. Parallel Query Processing in Shared Disk Database Systems Sigmod Record, 22(4): 32-37, Dec. 1993. Long version from:Proc. 5th Int. Workshop on High Performance Transaction Systems, Asilomar (CA), USA, Sep. 1993; 1993

Marek, R.; Rahm, E. Performance Evaluation of Parallel Transaction Processing in Shared Nothing Database Systems Proc. 4th Int. PARLE Conf. (Parallel Architectures and Languages Europe), Springer LNCS 605, pp. 295-310 1992

Rahm, E. A Framework for Workload Allocation in Distributed Transaction Processing Systems, The Journal of Systems and Software, Vol. 18, No. 3, 1992, pp. 171 - 190 1992

Bohn, V.; Härder, T.; Rahm, E. Extended Memory Support for High Performance Transaction Systems Proc. Messung, Modellierung und Bewertung von Rechensystemen (MMB) 1991

Rahm, E. Recovery Concepts for Data Sharing Systems, Proc. 21st Int. Symp. on Fault-Tolerant Computing Systems (FTCS-21), Montreal, June 1991, IEEE Computer Society Press, S. 368-375 1991

Rahm, E. Der Database-Sharing-Ansatz zur Realisierung von Hochleistungs-Transaktionssystemen Informatik-Spektrum, Vol. 12, No. 2, 1989, pp. 65 – 81 1989

Rahm, Erhard Synchronisation in Mehrrechner-Datenbanksystemen. Konzepte, Realisierungsformen und quantitative Bewertung Springer Informatik-Fachberichte 1988

Rahm, E. Design of Optimistic Methods for Concurrency Control in Database Sharing Systems. Proc. 7th Int. Conf. on Distributed Computing Systems, IEEE Computer Society Press, 154-161, Berlin, Sep. 1987 1987

Rahm, E. Integrated Solutions to Concurrency Control and Buffer Invalidation in Database Sharing Systems, in: Proc. 2nd Int.Conf. on Computers and Applications, IEEE Computer Society Press, pp. 410-417, Peking, June 1987 1987

Rahm, E. Primary Copy Synchronization for DB-Sharing. Information Systems 11 (4), 275-286, 1986 1986

Rahm, Erhard Concurrency Control in DB-Sharing Systems Proc. GI-Jahrestagung 1986

Härder, T.; Rahm, E. Quantitative Analyse eines Synchronisationsalgorithmus für DB-Sharing Proc. MMB 1985 1985