Re: Q: oracle data files & performance

At 11:34 AM 7/31/2005, Amihay Gonen wrote:
>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 ?

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.

>
>I'm talking only from performance perspective , not from backup & recovery ?
>
>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 ?

I am not certain of the answer. I have seen indications of both - well not exactly both, but uneven growth of the datafiles so not exactly strict round-robin extent allocation but also not exactly filling one file totally before using the other(s).

Counterquestion - is Oracle a He or a She - or an It or a hermaphrodite

Regards

Wolfgang Breitling
Centrex Consulting Corporation
http://www.centrexcc.com

--
http://www.freelists.org/webpage/oracle-l