Complex objects to support non-standard database applications require the use of substantial computing resources because their powerful operations and their related integrity constraints must be performed and maintained in an interactive environment. Since the exploitation of parallelism within such operations seems to be promising, we investigate the principal approaches for processing a query on complex objects (molecules) in parallel. A number of arguments favor methods based on inter-molecule parallelism as against intramolecule parallelism. Retrieval of molecules may be optimized by multiple storage structures and access paths. Hence, maintenance of such storage redundancy seems to be another good application area to explore the use of parallelism. Deferred update seems to be a bad idea, whereas concurrent update strategies incorporate salient application features. For performance reasons, we have chosen a multiprocessor system sharing an instruction addressable common memory which is used for buffer management, synchronization, and logging/recovery. Activation of concurrent requests is supported by a nested transaction concept which allows a safe and effective execution control within parallel actions of an operation.
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