RE: Q: oracle data files & performance
- From: "Kevin Closson" <kevinc@xxxxxxxxxxxxx>
- To: <breitliw@xxxxxxxxxxxxx>
- Date: Sun, 31 Jul 2005 12:12:04 -0700
>>>In Oracle no two processes write to the same datafile.
>>>Writing changed blocks to the files is the job of the db
>>>writer (dbwr) and thus a single process. Even if IO slaves
>>>are used, the dbwriter will collect all blocks for the same
>>>file and give them to a single slave to write.
Don't forget about foreground writes (direct path writes).
Shadow processes do these all the time for temp seg writes.
Nice optimization ,really.
Also, configuring more than one dbw (not to be confused with
dbwr io slaves) get a better degree of parallelism for clearing
dirty blocks...the dbwr work loop spends a lot of time
dealing with block metadata on cache buffers lru and chains...
along with the (potential) associated latch contention
>>>
>>>Counterquestion - is Oracle a He or a She - or an It or a
>>>hermaphrodite
I think you have a feeling for my answer to this one based
on my postings on the OakTable ... :-)
>>>
>>>
>>>Regards
>>>
>>>Wolfgang Breitling
>>>Centrex Consulting Corporation
>>>http://www.centrexcc.com
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