We continuously performed research on different aspects of Parallel database systems (PDBS) between 1985 and 2001. Early work focused 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).