FreeLists / oracle-l / Re: Q: oracle data files & performance

[zhu chao <zhuchao@xxxxxxxxx>]

 Hi , 
I've received a two interesting questions from a collage of mine.
 1)
If two processes are writing to the same file , will they suffer from some 
conation on the file handler ? 
Do you think that spreading very busy tables (has a lot of inserts from 
different sessions) on different tablespaces (which will be translate to 
different data files ) will have better I/O performance over one single data 
file ? 
 I'm talking only from performance perspective , not from backup & recovery 
?
 －－There is the so-called single file write lock in unix.
Raw volume/disk does not have this problem.
and solaris/AIX 5.3 now have feature called Concurrent IO, which also solves 
this problem.
 I am not sure, when we have several dbwr configured, whether different dbwr 
will write to the same datafile in the same time.
 2)
If we have tablespaces with several data files . Will oracle allocate 
extents in a round-robin fashion between the files or will he fill one data 
file and then pass to the another data file ?
  Oracle will write to the datafiles in a round robin fashion. You can 
create a tablespace with 3/5 datafile, and create atble, allocate extent, 
see how oracle distribute it among different datafiles.
  
 -- 
> Regards
> Zhu Chao
> www.cnoug.org <http://www.cnoug.org>
>