The performance of many object-oriented database applications suffers from the page fetch latency which is determined by the expense of disk access. In this work we suggest several prefetching techniques to avoid, or at least to reduce, page fetch latency. In practice no prediction technique is prefect and no prefetching technique can reduce the total demand fetch time. Therefore we are interested in the trade-off between the level of accuracy required for obtaining good results in terms of elapsed time reduction and the processing overhead needed to achieve this level of accuracy. If prefetching accuracy is high then the total elapsed time of an application can be reduced significantly otherwise if the prefetching accuracy is low, many incorrect pages are prefetched and the extra load on the client, network, server and disks decreases the whole system performance. Access pattern of object-oriented databases are often complex and usually hard to predict accurately. The main thrust of our work therefore concentrates on analysing the structure of object relationships to obtain knowledge about page reference patterns. We designed a technique, called OSP, which prefetches pages according to a time constraint established by the duration of a page fetch. In addition, every page has an associated weight that decides about the execution of a prefetch. We implemented OSP in the EXODUS storage manager by adding multithreading to the database client. The performance of OSP is evaluated on different machines in interaction with buffer management, distributed databases and other system parameters.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:653495 |
| Date | January 1999 |
| Creators | Knafla, Nils |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/10999 |
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