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notes on 'expert oracle'-no.4: memory areas-chenjianjx的专栏-iteye技术网站

 
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notes on 'expert oracle'-no.4: memory areas-chenjianjx的专栏-iteye技术网站
2011年09月01日
   1.SGA & PGA
  a. SGA: Shared Area for all the processes/threads 
  b. PGA: The area for a single process/thread 
  SGA ∩ PGA == 
  2.UGA: The area for the user  
  a. UGA SGA if "Shared Server" is used. 
  b. UGA PGA if "Dedicated Server" is used. 
  3.Important components of SGA 
  a.Redo Buffer -- extremely helpful for big/long transactions, since the redo log is involved for transactions. 
  b.Block Buffer Cache -- Caching query results 
  c.Shared Pool -- 
  i. Bascially for compiled SQLs. So, always use "Bind variables" in SQLs because this way there will be too much SQLs in this pool(Think otherwise). 
  ii.LRU-Cache 
  d.Large Pool  -- For large memory alloacation 
  4.SQLs for SGA
  a. See pools 
  select * from V$SGASTAT 
  b. See pool size 
  select sum(bytes)/1024/1024 mbytes from V$SGASTAT where pool = 'shared pool' 
  
  
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