RE: Physical Reads and Writes

  • From: "Allen, Brandon" <Brandon.Allen@xxxxxxxxxxx>
  • To: Bill Zakrzewski <bill@xxxxxxxxxxxx>, ORACLE-L <oracle-l@xxxxxxxxxxxxx>
  • Date: Fri, 28 Aug 2009 13:13:33 -0700

Maybe unlikely, but not impossible - just because the database is 300GB doesn't 
mean that users weren't only querying a small portion of it (e.g. just the most 
current data) at the time when you were running the sar command.  I also work 
with several DBs in that same size range, but most of it is historical and 
probably less than 5% of the blocks are used on a regular basis - that's how we 
get by with just a 3GB buffer cache  on a 300GB database.  I'm not trying to 
say that all your blocks are cached, just saying that I wouldn't ignore it as a 
real possibility so I'd recommend digging deeper to see if it's actually the 
case or not.


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