I/O
17.07.2015

db file scattered read – MBRC and ASYNC IO on linux

Recently one of my students asked me if there is any correlation between the AU size in ASM diskgroup and parameter db_file_multiblock_read_count. I made some tests but results are very strange. I have 4 same tables, located in 4 different diskgroups: All tables are smaller then a hidden parameter "_small_table_threshold" so table access full on […]


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12c (Spatial)
03.05.2015

12c: Spatial Vector Acceleration

There is a new feature in Oracle Spatial 12c, called "Spatial Vector Acceleration". According to Oracle: One of the most notable improvements with Oracle Spatial and Graph 12c can be seen in performance increases in vector data operations. Enabling the Spatial Vector Acceleration feature (available with the Spatial option) dramatically improves the performance of commonly […]


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TUNING
10.10.2014

Oracle 11g & 12c: tunning the sort and hash operations

Hash and sort operations are perfomed in PGA. Quoting after the documentation: A sort operator uses a work area (the sort area) to perform the in-memory sorting of a set of rows. Similarly, a hash-join operator uses a work area (the hash area) to build a hash table from its left input. If the work […]


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TUNING
26.09.2013

Oracle CBO. Query Transformer

Oracle Cost Based Optimizer consists of three main components: Query Transformer, Esitmator, Plan Generator. In this article I will try to show you some interesting features of the first component – Query Transformer. This component has some very powerful features and most of them remain in shadows, unrevealed while other new features gains all the […]


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TUNING
10.06.2012

library cache: mutex X i CURSOR_SHARING=FORCE:

Prowdząc niedawno optymalizację wydajności jednego RACa, natknąłem się na ciekawe zachowanie w trakcie parsowania zapytań odwołujących się w predykacie do typu TIMESTAMP – niecodzienne zachowanie dotyczy ustawienia CURSOR_SHARING=FORCE i bazy 11.1.0.7 oraz 11.2.0.2. Problem opisłem na forum GoldenLine – jeśli spotkaliście się z podobnym problemem lub znaleźście jakiegoś patcha – zachęcam do podzielenia się tą […]


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