The Oracle (tm) Users' Co-Operative FAQ
How does Oracle handle PGA memory.
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Author's name: Jonathan Lewis Author's Email: jonathan@jlcomp.demon.co.uk |
Date written: 14th Sept 2005 Oracle version(s): 9.2.0.6 |
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Sorts, hash joins, bitmap creation, and bitmap merges are memory intensive operations, and Oracle introduced a new strategy for handling large memory allocations in 9i. Is there a convenient summary of how the old and new mechanisms differ. |
This question is addressed by the following documents:
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Christo Kutrovsky |
Jonathan Lewis |
When trawling the internet recently to see what had been published about the pga_aggregate_target, I found this powerpoint presentation (660KB). It was probably one of the most useful documents I found. Apart from anything else, it started with a good graphic on virtual memory mapping and where the memory goes. Well worth reading. The slides include details from the original paper (below) by Benoit Dageville and Mohamed Zait, and a couple of fascinating little points about how hash joins can play clever games with automatic workarea sizing. |
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Benoit Dageville and Mohamed Zait |
Jonathan Lewis |
The definitive guideline to what it’s all about. A pdf file of a paper published for the VLDB conference in 2002. |
Further reading: (probably the best thing here is a reference to the relevant bits of the Oracle manuals)
